Diagnosis and Management of Obstetrical
Complications Unique to Multiple Gestations
George M. Graham III, MD,* and Sreedhar Gaddipati, MD†
Obstetrical complications unique to multiple gestations pose a number of unique challenges.
The presence of more than one fetus complicates the diagnosis and management of a pregnancy when one fetus has a structural or chromosomal abnormality, intrauterine demise,
preterm premature rupture of the membranes, or delivers prematurely. Similarly, the diagnosis
and management of monoamniotic twins and conjoined twins is challenging. These obstetrical
complications that are unique to multiple gestations require thorough counseling of the
expectant parents, as well as care by physicians with expertise in the management of multiple
gestations.
Semin Perinatol 29:282-295 © 2005 Elsevier Inc. All rights reserved.
KEYWORDS discordant fetal abnormality, intrauterine fetal demise, premature rupture of the
membranes, delayed interval delivery, monoamniotic twins, conjoined twins
C
ommon obstetric complications, such as preeclampsia,
gestational diabetes, preterm labor, and intrauterine fetal growth restriction, occur more frequently in multiple gestations, yet the diagnosis and management of these conditions are similar as for singleton pregnancies. In contrast,
unique challenges arise when one fetus in a multiple gestation has a structural or chromosomal abnormality, intrauterine demise, preterm premature rupture of the membranes, or
delivers prematurely. The presence of more than one fetus in
utero confounds the diagnosis and management of these serious obstetric complications. Furthermore, multifetal gestations are at increased risk for complications that are unique to
monochorionic gestations, such as twin–twin transfusion
syndrome, monoamnionicity, twin reversed arterial perfusion syndrome, and conjoined twins. This chapter addresses
the management of some of these complications that are
unique to multiple gestations.
Discordant Fetal Abnormalities
Diagnosis of an Abnormal Fetus
A single fetus in multiple gestation may be affected by both
chromosomal and structural abnormalities. In a dizygotic
*Department of Obstetrics and Gynecology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI.
†New York Presbyterian Hospital, Columbia University, College of Physicians and Surgeons, New York, NY.
Address reprint requests to George M. Graham III, MD, Department of
Obstetrics and Gynecology, John A. Burns School of Medicine, University of Hawaii, 1319 Punahou Street, Honolulu, HI 96826. E-mail:
ggraham@hawaii.edu
282
0146-0005/05/$-see front matter © 2005 Elsevier Inc. All rights reserved.
doi:10.1053/j.semperi.2005.10.003
pregnancy, each fetus has its own independent risk for a
chromosomal or structural abnormality, so the overall risk of
an abnormality increases as the number of fetuses increases.
The risk of a chromosomal abnormality in a monozygotic
multiple gestation is similar to the risk in a singleton. However, monozygotic gestations are at an increased risk of complications that are unique to monochorionic gestations, such
as twin–twin transfusion syndrome, twin reversed arterial
perfusion syndrome, and conjoined twins.
The goals of prenatal diagnosis in a multiple gestation are
the same as a singleton: to identify fetal abnormalities that
could lead to a couple’s decision to terminate a pregnancy or
alter the management of the pregnancy and delivery, and to
identify fetuses that might benefit from fetal or early neonatal
therapy. However, prenatal diagnosis in multiple gestations
poses a number of unique challenges. Maternal serum
screening is not as reliable in twins and may not be interpretable in higher-order multiples. Invasive diagnostic procedures, such as chorionic villus sampling and amniocentesis,
are technically more challenging in multifetal gestations. Finally, the presence of multiple fetuses makes the assessment
of fetal anatomy at the time of prenatal ultrasound more
difficult. For a more thorough review of prenatal diagnosis in
multiple gestations, the reader is referred to the chapter by
Drs. Cleary-Goldman, D’Alton, and Berkowitz.
Management of
Discordant Fetal Abnormalities
When fetal abnormalities are detected in one fetus of a previable multiple gestation, couples can choose between termi-
Complications unique to multiple gestations
nation of the entire pregnancy, expectant management, or
selective termination of the abnormal fetus. When the abnormality is diagnosed after viability, the options are limited
depending on the jurisdiction and the extent of the abnormality. For example, as in a singleton pregnancy, the third
trimester termination of an anencephalic fetus in a multiple
gestation may be considered.1,2 Termination of the entire
pregnancy in a multifetal gestation, as in a singleton gestation, can be performed surgically or by prostaglandin induction.
Expectant management should be pursued only after a
thorough discussion and documentation of the risks of continuing the pregnancy. It is important that the patient be
informed of how the anomalous fetus might affect the prognosis for the entire pregnancy. In a monochorionic pregnancy, counseling should include the risks to the normal
cotwin in the event of a demise of the abnormal fetus. Regardless of chorionicity, an abnormal fetus may increase the
risk of miscarriage or preterm delivery through complications such as polyhydramnios. The management of labor, in
particular intervention for nonreassuring fetal status or malpresentation of the anomalous fetus, should be defined before delivery.
Selective termination should be offered when a fetal anomaly is detected before viability in a multifetal gestation. The
benefits of selective termination need to be weighed against
the procedure-related risk of miscarriage or premature delivery. Selective termination in multichorionic pregnancies is
most commonly performed by fetal intracardiac injection of
potassium chloride. In a multicenter study of 402 selective
reductions by intracardiac or intrafunic injection of postassium chloride, the overall rate of pregnancy loss before 24
weeks was 7.5%.3 The pregnancy loss rates based on the
gestational age at the time of the procedure were 5.4% when
the procedure was performed between 9 and 12 weeks, 8.7%
between 13 and 18 weeks, 6.8% between 19 and 24 weeks,
and 9.1% when the procedure was performed beyond 25
weeks. These differences were not statistically significant,
suggesting that the risk of pregnancy loss following selective
termination is similar in all trimesters. Further support for
the safety of second trimester selective reduction comes from
a study that reported similar loss rates following multifetal
reduction in the first trimester and selective termination in
the second trimester.4 In monochorionic pregnancies, selective reduction using an intracardiac injection of postassium
chloride can result in demise of the cotwin either by transplacental passage of potassium chloride or acute hemodynamic changes in the untreated fetus.3 For this reason, a
number of methods involving cord ligation and coagulation
have been developed for performing selective termination in
monochorionic pregnancies.5 For a more thorough review of
the methods of selective reduction in monochorionic multifetal gestations, the reader is referred to the chapter by Drs.
Spadola and Simpson.
The diagnosis of an abnormal fetus in a multiple gestation
creates a complex set of circumstances for a family that must
decide between termination of the entire pregnancy, expectant management, or selective reduction of the abnormal fe-
283
tus. Furthermore, these cases are challenging for physicians
involved in the counseling and management of such patients.
There are ethical challenges that require an appreciation for
beneficence and respect for autonomy of both the mother
and the fetuses.6 Before viability, a fetus can only be considered a patient if the mother confers that status on the previable fetus, including the fetus with an anomaly. As such,
respect for the autonomy of the mother is the guiding principle. When a woman chooses selective termination, she is
withholding the status of becoming a patient from the fetus
with the abnormality, but not the other normal fetuses. Because the risk of selective termination to the remaining fetuses is minimal, the procedure does not violate the beneficence-based obligation to the remaining fetuses. After
viability, the ethical standard of care is to optimize perinatal
outcome through aggressive antepartum and intrapartum
management. However, other options that could be considered include selective termination and nonaggressive management of the pregnancy. Selective termination of a viable
abnormal fetus is only ethical when there is certainty of the
diagnosis, and certainty of death or absence of cognitive development as an outcome of the anomaly.1,7 When the diagnosis and/or prognosis are less certain, both the physician
and the mother have a beneficence-based obligation to the
viable fetus. Nonaggressive management should be reserved
for cases in which there is a high probability of death or
absence of cognitive function, but not certainty of the diagnosis and prognosis.7,8 However, nonaggressive management
may not be appropriate when an abnormal fetus shares a
placenta with a normal fetus. In such a case, nonaggressive
management might place the normal fetus at risk and, for this
reason, challenges the beneficence-based obligation to the
normal fetus.
Intrauterine Demise of One
Fetus in a Multiple Gestation
The increasing use of ultrasonography in early pregnancy has
revealed that the incidence of a spontaneous multiple gestation is greater than previously believed. In fact, twin gestations may occur in as many as 12% of all spontaneous conceptions.9 However, it is estimated that only 50% of twin
pregnancies identified in the first trimester will result in two
live born infants.10 In some cases the entire pregnancy will be
lost, and in other cases only one embryo will be lost and the
pregnancy will continue as a singleton gestation. When one
embryo in a multiple gestation is lost, this is known as a
“vanishing twin.”9
Risks to the Surviving Fetus(es)
Following the Demise of One Fetus
Although the loss of one embryo in a multiple gestation is
common in the first trimester, most patients are asymptomatic or have only slight vaginal spotting following the loss.11
Fortunately, when the demise occurs early in pregnancy, it
appears that the prognosis for the surviving fetus(es) is excellent.9,10,12
284
On the other hand, second and third trimester loss of a
fetus in a multiple gestation has been associated with adverse
outcomes. The demise of one fetus in a multiple gestation at
this time is relatively rare, complicating anywhere from 2% to
5% of twin pregnancies.13-15 Late demise of both fetuses in a
twin pregnancy occurs infrequently.16 It is estimated that
there is a threefold to fourfold increase in intrauterine death
with monochorionic twins compared with dichorionic
twins.15,17 Twins with structural malformations are more
likely to die in utero than their anatomically normal
cotwins.15 The intrauterine demise of a single fetus is more
common in higher-order multiple gestations, complicating
14% to 17% of triplet pregnancies.18,19 Intrauterine demise of
one fetus in a multifetal gestation increases the risk for adverse events in the surviving fetus(es).20,21
The greatest risk to the surviving fetuses regardless of chorionicity is preterm delivery and the associated complications
of prematurity. Overall 50% to 80% of surviving cotwins are
delivered before term, and of these premature deliveries,
86% are due to preterm labor.12-14 However, for monochorionic twins, there is the additional risk of multiorgan damage
in the surviving cotwin. Ischemic injury has been documented in the spleen, kidney, gastrointestinal tract, skin, and
brain of surviving cotwins.22-26 It is estimated that up to 20%
of the surviving fetuses in monochorionic twin pregnancies
may experience neurologic injury, such as multicystic encephalomalacia. Multicystic encephalomalacia is the development of cystic lesions in the cerebral white matter in areas
supplied by the anterior and middle cerebral arteries. While
the exact mechanism of neurologic injury is uncertain, it is
thought to be related to the shared vasculature in monochorionic pregnancies. The extent of shared placental vasculature likely influences the degree to which a surviving twin
will be affected by demise of its cotwin. There are two main
theories regarding the pathophysiology of neurologic injury
in surviving monochorionic twins. An early theory was that
the retained fetus creates thromboplastic materials that embolize through placental anastomoses to the surviving twin.17
A more recent and widely accepted theory is that the sudden
decrease in blood pressure that occurs at the time of fetal
death results in “back-bleeding” from the live twin to the
dead twin’s vasculature, causing transient but severe hypotension and hypoxemia in the surviving fetus.13 This theory
has been supported by the development of anemia with normal
coagulation studies in the cotwin following an intrauterine fetal
demise of a single fetus in a monochorionic pregnancy.27,28
Given that the changes in pressure are likely instantaneous
with fetal death, it is not surprising that immediate delivery
does not prevent the development of multicystic encephalomalacia in the surviving twin. In fact, immediate delivery may
increase the risk to the surviving cotwin through the complications of prematurity.
In dichorionic twin pregnancies, the risk of major perinatal morbidity or mortality to the surviving twin appears to be
negligible apart from that related to preterm delivery.13 Dichorionic twins complicated by a single intrauterine demise
do not seem to be at increased risk of neurologic injury, other
than the risks related to prematurity.13 The surviving twin in
G.M. Graham III and S. Gaddipati
a dichorionic pregnancy is likely protected from ischemic
injury because of the separate vascular systems.
In addition to the potential risks to the surviving fetus(es)
following the demise of a single fetus in a multiple gestation,
there is the potential for maternal complications as well. In
multiple gestations, similar to singletons, retention of a dead
fetus has been estimated to result in a 25% incidence of
maternal disseminated intravascular coagulation.9 However,
only a few cases of maternal coagulopathy have been reported
under these circumstances, so the 25% incidence is likely an
overestimation. In a review of 16 pregnancies complicated by
intrauterine fetal death of 1 twin, there were no cases of
maternal disseminated intravascular coagulation.13 While
transient fibrin-split products and hypofibrinogenemia have
been observed in some twin pregnancies complicated by demise of one fetus, medical therapy or intervention was not
necessary.14 Although the maternal risk appears to be low,
periodic coagulation profiles are recommended to detect the
early development of this complication. Following the demise of a cotwin, mothers do not appear to be at increased
risk of infection as a result of the retained fetus; however,
there is an increased risk of delivery by cesarean section secondary to nonreassuring fetal status.29 In addition, there are
psychological considerations for the parents following the
death of one fetus in a multiple gestation. Although the psychological impact of an intrauterine demise in a singleton
pregnancy has been described, less is known about the effects
of losing a fetus in a multiple gestation.30 Feelings of loss
could be complicated by concerns over well-being for the
surviving fetus(es), as well as relief that the entire pregnancy
was not lost. Providers should be aware that the parents’
response to the loss of a single fetus in a multiple gestation is
complex and that these families may benefit from counseling
by a therapist with experience in high-risk pregnancies.
Management of a Multifetal Gestation
Complicated by a Single Fetal Demise
After the demise of one fetus in a multifetal pregnancy, the
clinical management is challenging and depends on chorionicity, gestational age, fetal lung maturity, and the development of fetal or maternal complications. The optimal timing
of delivery and the frequency with which antenatal testing
should be performed are controversial. Management strategies can be based on the chorionicity and whether the demise
occurs before or after fetal viability. Regardless of the gestational age and chorionicity, multifetal gestations that are
complicated by an intrauterine demise of one fetus need to be
followed closely for the development of preterm labor.
When the demise occurs before viability, the management
of a dichorionic twin pregnancy consists of expectant management until 37 weeks’ gestation. Steroids for fetal lung
maturity and surveillance for preterm labor, fetal well-being,
and fetal growth should be considered until viability is
reached. The management of previable monochorionic twin
pregnancies after the demise of one fetus is more complicated. Parents should be counseled about the risks of multiorgan injury, including multicystic encephalomalacia, and
Complications unique to multiple gestations
our inability to predict with certainty whether a surviving
cotwin will be affected. Serial ultrasounds and magnetic resonance imaging (MRI) may be useful to detect multicystic
encephalomalacia antenatally. When demise occurs in a
monochorionic previable twin pregnancy, termination of the
pregnancy should be offered.
Intrauterine demise of one fetus after viability, regardless
of chorionicity, is not an indication for delivery. Administration of corticosteroids to enhance fetal lung maturity between
24 and 34 weeks is reasonable given the increased risk of
preterm delivery. In dichorionic pregnancies, weekly assessment of fetal well being is reasonable. Increased fetal surveillance should be considered if other complications, such as
growth restriction or oligohydramnios, develop. Again, the
management of monochorionic twins is more complicated
because it is difficult to predict whether the surviving fetus
will develop cerebral damage. When neurologic injury develops, it is thought to occur at the time of death of the cotwin.11
For this reason, immediate delivery of the surviving twin
does not appear to change the outcome. Again, steroids for
fetal lung maturity should be considered for gestational ages
between 24 and 34 weeks. Frequent assessment of fetal wellbeing is recommended. Serial ultrasounds and MRI, performed approximately 2 to 3 weeks after the demise, may be
useful to detect multicystic encephalomalacia antenatally.
However, it is important for parents to understand that close
fetal surveillance cannot guarantee an intact fetus. In general,
elective delivery should be considered at 37 weeks’ gestation
or once fetal lung maturity is demonstrated. Delivery by cesarean section should be performed for routine obstetric indications, as vaginal delivery is not contraindicated in this
situation.13 In monochorionic pregnancies with impending
demise of one twin, preterm delivery may be indicated to
prevent neurologic injury to the survivor or to potentially
salvage both twins.
Autopsy of the still born fetus should be offered and pathological examination of the placenta(s) should be performed to
confirm chorionicity. Monochorionic twin survivors should
be followed closely by their pediatrician for any evidence of
neurologic injury or organ damage.21
Preterm Premature
Rupture of the Membranes in
One Fetus of a Multiple Gestation
Incidence and Diagnosis of
Membrane Rupture in a Multiple Gestation
Preterm premature rupture of membranes (PPROM) is a
complication in one-quarter to one-third of all preterm
births, making it a leading cause of infant mortality and morbidity. PPROM affects 10% of all pregnancies, including multiple gestations. Whereas there is extensive literature on the
clinical course of singleton pregnancies complicated by
PPROM, there are limited data on PPROM in multiple gestations. As a result, the optimal management of this complication in multiple gestations is not clear and clinical decisions
285
are compounded by the presence of one or more fetuses with
intact membranes. The approach to PPROM in a multiple
gestation involves a balancing of risks to both fetuses in the
ruptured and unruptured sacs, as well as the mother.
The incidence of PPROM in multiple gestations is twice
that of singleton pregnancies.31 In a retrospective review of
multiples between 19 and 36 weeks’ gestation, PPROM complicated 7.4% of twin pregnancies compared with 3.7% of
singleton pregnancies.31 The incidence of PPROM in triplets
was similar to that in twins at 7.4%.31 PPROM in the midtrimester of pregnancy also occurs more frequently in twins
(1.4%) compared with singletons (0.5%).31 In the majority of
cases of PPROM in multiple gestations, rupture occurs in the
presenting amniotic sac, and the diagnosis is easily confirmed
on clinical evaluation of vaginal pooling, ferning, nitrazine
testing, and ultrasound assessment of amniotic fluid volume.
The diagnosis can be more difficult when PPROM of the
nonpresenting sac occurs, as leakage of fluid from the vagina
may be intermittent. The exact incidence of PPROM in a
nonpresenting sac is unknown, but it is thought to be limited
to complications related to invasive procedures, such as amniocentesis or fetal blood sampling. Information on the incidence of PPROM in multiples based on chorionicity is also
unknown. A complication that is unique to monochorionic,
diamniotic twin pregnancies is rupture of the dividing membrane.32 This can result in a twin pair sharing an amniotic sac,
with all the risks associated with monoamniotic twins. Usually this complication follows an invasive procedure, such as
an amniocentesis. However, in some cases, there is no precipitating event to explain the finding of a monoamniotic
gestation that was previously diamniotic. Although the exact
incidence of diamniotic gestations becoming monoamniotic
is unknown, spontaneous rupture of the separating membrane is likely a rare event. In addition to invasive procedures, rupture of the separating membrane in a multiple
gestation may be the result of infection or disturbances in
membrane development.32 The resultant monoamniotic
pregnancies have been complicated by preterm delivery,
with an average gestational age at delivery of 29 weeks, and
an increased risk of perinatal death with an overall perinatal
mortality of 44%.32
Latency and Risks Following
Premature Rupture of the Membranes
Overall, the latency period between rupture of membranes
and delivery of expectantly managed twins and singletons is
similar. For twin gestations with PPROM between 19 and 36
weeks, Mercer and coworkers reported a median latency of
1.1 days.32 Of 91 twin pairs, 64% delivered within 48 hours,
and 91% delivered within 7 days of membrane rupture.31
These observations were not significantly different from
those observed in singleton gestations, which had a median
latency of 1.7 days, with 90% delivered at 7 days.31 In a
comparison of 116 twins with PPROM to matched singleton
controls, the median latency period in twins was 11.4 hours
compared with 19.5 hours in singletons.33 The shorter latency in twins was not clinically significant, as the proportion
286
of twins and singletons delivered at 48 hours and 7 days was
similar.33
As in singleton pregnancies, the duration of the latency
period in multiple gestations is related to the gestational age
at the time of membrane rupture. Latency is significantly
prolonged when PPROM occurs before 30 weeks’ gestation
for both singletons and twins. In a comparison of 48 twins to
131 singletons, the latency periods were similar when
PPROM occurred before 30 weeks’ gestation (4.8 days versus
5.6 days).34 When PPROM occurred after 30 weeks, latency
for twins was significantly shorter than that of singletons (2.5
days versus 3.7 days).34 Another study found that twins had
a significantly shorter latency period, regardless of gestational
age. In a matched comparison of 116 twins and 116 singletons with PPROM, a significantly shorter latency period was
found in twins overall (11.4 hours versus 19.5 hours).33 In
addition, twins had a significantly shorter latency than singletons when PPROM occurred before 30 weeks (27.6 hours
versus 75.1 hours).33 Despite the shorter latency for twins
compared with singletons, there were no significant differences in neonatal outcomes between the two groups.33
Both singleton and twin pregnancies complicated by
PPROM are at increased risk for infection, cord accidents,
and placental abruption. Mercer and coworkers found no
significant difference in the incidence of amnionitis (15%
versus 23%), cord prolapse (4% versus 2%), or placental
abruption (1% versus 6%) between singleton and twin pregnancies.17 Overall, there are no differences in perinatal morbidity or mortality between singletons and twins with
PPROM.33,34 However, significant differences in neonatal
morbidity have been reported between the presenting and
nonpresenting fetuses.31 In twin pregnancies complicated by
PPROM, the nonpresenting twin is at increased risk for respiratory distress syndrome (20.9% versus 7.1%) and prolonged oxygen therapy (43.6% versus 22.6%) when compared with the presenting twin.31 It is unknown whether this
reflects accelerated fetal lung maturity after PPROM in the
presenting twin or a relative immaturity in the nonpresenting
twin. The finding of increased respiratory morbidity and
lower Apgar scores in the nonpresenting twins does not appear to be related to the route or mode of delivery.31 Despite
PPROM of the presenting sac, there were no statistical differences in infectious morbidity between the presenting and
nonpresenting twins.31 Based on these findings, patients
should be counseled that the nonpresenting fetus appears to
be at higher risk for respiratory complications following
PPROM of the presenting fetus.
The most critical aspect to consider in the management of
PPROM in multiple gestations is the gestational age at the
time of membrane rupture. It is important to weigh the risks
of prematurity versus the risks of infection and the potential
adverse effects of oligohydramnios. Infectious complications
from PPROM may affect the mother, the fetus in the ruptured
sac, as well as the cofetus(es) with intact membranes. The
risks of oligohydramnios pertain to the fetus in the ruptured
sac, and these are dependent on gestational age and the
amount of remaining amniotic fluid. Oligohydramnios early
in gestation may be associated with the development of pul-
G.M. Graham III and S. Gaddipati
monary hypoplasia, skeletal deformities, and amniotic band
syndrome.
Management of PPROM
in a Multiple Gestation
PPROM can be classified as previable (before 23 completed
weeks’ gestation), remote from term (23 to 31 weeks’ gestation), and near term (32 to 36 weeks’ gestation). The contemporary management of singletons with PPROM is well established and can be applied to multiple gestations.35 Regardless
of gestational age, once the diagnosis of PPROM is confirmed,
digital examinations of the cervix should be avoided to increase latency and decrease infectious morbidity.35 Visualization of the cervix by sterile speculum should be performed, at
which time appropriate cultures can be obtained. Patients
should then be carefully evaluated for any evidence of advanced labor, infection, placental abruption, and nonreassuring fetal status. Apart from nonreassuring fetal status at a
previable gestational age, the development of these complications warrants expeditious delivery.35
The management of multiple gestations with PPROM near
term is similar to that of singletons. When PPROM occurs
after 34 weeks, the perinatal complications related to prematurity are outweighed by the risks of chorioamnionitis and
fetal loss due to cord compression, and therefore delivery is
recommended.35 Antibiotic prophylaxis for group B streptococcus should be given if culture results are not available, or
broad-spectrum antibiotics if there is any evidence of intrauterine infection. PPROM in multiple gestations between 32
and 34 weeks warrants delivery if fetal lung maturity is documented on amniotic fluid from vaginal pooling or from
amniocentesis from the fetus with the ruptured sac, and by
amniocentesis from the sac of the other fetus(es). If fetal lung
maturity studies are negative, discordant, or if fluid is not
available from all fetuses, then conservative management
with close fetal surveillance and maternal monitoring as an
inpatient are recommended. Consideration should be given
to adjunctive antibiotic therapy to treat or prevent ascending
infection to prolong the pregnancy.35 The effect of steroids on
fetal lung maturity in multiple gestations has not been studied. Antenatal corticosteroids may be administered to gravidas with PROM up to 34 weeks of gestation.36 Tocolysis is not
generally used at this gestational age because the risk of significant perinatal morbidity is low.35 In the absence of labor,
placental abruption, nonreassuring fetal testing, or chorioamnionitis, delivery should be considered once 34 weeks of
gestation is reached.
Similarly, the management of multiples with PPROM remote from term parallels that of singletons. When PPROM
occurs between 23 and 31 completed weeks, conservative
management is recommended to prolong the pregnancy
since delivery before 32 weeks is associated with significant
risks of neonatal morbidity and mortality.35 Inpatient fetal
and maternal surveillance, a single course of antenatal corticosteroids, and antibiotics to prolong latency are all recommended.35 Ideally, conservative management of multiple gestations complicated by PPROM should be performed at
Complications unique to multiple gestations
centers that are capable of performing immediate cesarean
deliveries and providing appropriate neonatal care. If necessary, patients should be transferred early in the course of
management to avoid emergent transfer in the event that
complications develop.35 Although data regarding the role of
tocolysis in multiple gestations with PPROM are lacking, the
use of prophylactic tocolytics to prolong pregnancy and allow time for the benefits of corticosteroids and antibiotics is
reasonable.35 Again, in the absence of labor, placental abruption, nonreassuring fetal testing, or chorioamnionitis, delivery should be considered once 34 weeks of gestation is
reached or between 32 and 34 weeks if fetal lung maturity is
documented for each fetus.35
In contrast to PPROM remote from term or near term,
strategies for managing PPROM in multiple gestations at
previable gestational ages are less uniform than those for
singleton pregnancies. Currently, there are no data with
which to make recommendations regarding initial conservative management in these cases. Options for previable
PPROM range from expectant management to termination of
the entire pregnancy. Patients should be counseled about the
maternal and fetal risks and benefits of expectant management versus termination, and consent for any management
plan should be obtained. If termination is declined, outpatient management after initial observation in the hospital to
exclude infection or abruption is a reasonable option.35 As in
singleton pregnancies with PPROM, infection must be excluded and prompt delivery for any evidence of intrauterine
infection is recommended.35 Weekly visits to assess maternal
and fetal status should be performed until fetal viability is
reached. Once viability has been obtained, patients are usually readmitted to the hospital for closer maternal and fetal
surveillance. Psychological support should be made available
for patients and their families when faced with the difficult
management choices and decisions dealing with PPROM in
multiple gestations at previable gestational ages.
Investigational strategies, including selective reduction of
the fetus in the ruptured sac or preterm delivery of this fetus
followed by aggressive attempts to retain the remaining fetuses, have been reported when PPROM complicates a previable multiple gestation. Selective reduction of a previable
fetus following rupture of membranes in a multiple gestation
was first described by Dorfman and coworkers.37 This approach was based on the assumption that the risk of ascending infection would be reduced if the continuous leakage of
amniotic fluid from the ruptured fetus was eliminated, and
that a lower risk of infection would lead to an improved
chance of the pregnancy progressing to viability. De Catte
and coworkers reported on the outcome of 12 pregnancies in
a comparison of expectant management versus selective reduction in multichorionic multiple pregnancies with PPROM
between 13 and 20 weeks’ gestation.38 In 9 cases, patients
were managed expectantly without antibiotics or tocolytics.
Selective termination was performed in 3 cases within 3 days
of membrane rupture, followed by a 5-day course of antibiotics. Weekly steroids were administered beginning at 24
weeks’ gestation. The mean interval between membrane rupture and delivery in the expectantly managed group was 7.4
287
weeks with only 3 survivors. In the selective reduction group,
2 of the 3 pregnancies progressed beyond 33 weeks. Although the numbers are small, selective reduction of a previable fetus in a ruptured sac of a multichorionic gestation may
be a reasonable option in carefully selected cases; however,
further study is needed before this strategy can be recommended.
Aggressive approaches to prolong pregnancy in cases of
previable PPROM include the use of tocolytic therapy, antibiotics, and cervical cerclage. In a series of 8 multifetal gestations complicated by PPROM before 24 weeks’ gestation,
Arias and coworkers reported on efforts to delay delivery of
the retained fetuses after delivery of the ruptured fetus.39
Broad-spectrum antibiotics were administered, and, after delivery of the presenting fetus, either spontaneously or by
induction, the umbilical cord was ligated as high as possible
within the cervical canal. Tocolytics were given for uterine
contractions and a cerclage was placed once contractions
ceased. Prophylactic tocolysis with indomethacin was then
administered for 48 to 72 hours and antibiotics were continued for 1 week, after which time patients were discharged to
home. The authors reported a mean latency of 48 days. Although this aggressive approach successfully delayed delivery of the retained fetuses, subsequent reports by this same
group suggested less favorable results.39
The optimal management of previable PPROM in multiple
gestations remains unclear. Expectant management results in
an extremely high pregnancy loss rate and exposes the
mother to the risks of infection and the complications of
prolonged bed rest. In addition, pregnancies that progress to
fetal viability are still subject to high neonatal morbidity and
mortality from oligohydramnios, infection, and prematurity.
Given the complexities of previable PPROM, an individualized approach is recommended. In certain circumstances,
termination of the entire pregnancy may be the best approach. Although aggressive interventions, such as tocolysis
and cerclage after delivery of a previable fetus with PPROM,
may be considered, the benefits of these techniques need to
be adequately demonstrated before they can be recommended. Similarly, selective reduction, which appears to
have a higher success rate than expectant management, requires further study.
Preterm Delivery of One Fetus
Delayed Interval Delivery
Following Preterm Delivery
of One Fetus in a Multiple Gestation
One of the most common and serious complications of multiple gestations is preterm delivery. In the majority of cases,
the remaining fetus(es) usually delivers soon after the presenting fetus is born. However, in rare circumstances, preterm delivery of one fetus may occur without spontaneous
delivery of the remaining fetus(es). This unique event raises
the possibility of prolonging a pregnancy to a more advanced
gestational age before delivery of the remaining fetus(es). The
older literature on delayed interval delivery was primarily
288
limited to case reports and, as such, was subject to bias of
only reporting favorable outcomes. More recently, larger case
series have been published. The largest series from a single
practice is a review of 24 consecutive interval deliveries involving twin and triplet gestations.40 In this series, a uniform
approach of tocolysis, antibiotics, and cerclage was used.
These authors reported a mean interval delivery time of 36
days, with a range of 3 to 123 days. Although there were no
survivors in the 16 first-born fetuses that delivered before 24
weeks’ gestation, 8 of the 18 retained fetuses in this group
survived. In the 9 pregnancies in which the first-born delivered after 24 weeks, 4 infants survived. Of the 9 retained
fetuses in this group, all survived. Overall, the perinatal mortality rate of first-born infants, regardless of gestational age,
was 84%. The perinatal mortality rate of the infants born after
delayed delivery was significantly less at 37%. In contrast to
this favorable outcome, a series of 14 cases of attempted
delayed interval delivery over a 12-year period reported less
encouraging results.41 In this retrospective study, the median
latency was only 2 days, with a range of less than 1 to 70 days.
There was only 1 survivor among the first-born fetuses. Of
the 19 retained fetuses, 7 survived until hospital discharge;
however, only 1 of these neonates was discharged without
major neurologic sequelae. Maternal morbidity included 2
cases of placental abruption and 8 cases of infectious morbidity, 1 of which resulted in septic shock and multiorgan
failure. This study raises serious concerns about the fetal
outcome and maternal risks associated with a delayed interval delivery; however, both studies are limited by a small
number of cases. A second limitation of these studies is that
they both include cases that were collected since 1991 and,
therefore, may not represent contemporary outcomes because of improved perinatal care.
Two larger retrospective cohort studies using the
“matched multiple birth file” prepared by the Centers for
Disease Control and Prevention’s National Center of Health
Statistics were recently published. This database includes information on all twin live births, still births, and infant deaths
in the United States during the period of 1995 to 1998. One
study identified 200 delayed twin deliveries in which the first
twin was delivered between 17 and 29 weeks’ gestation.42 In
this series, there was a significant improvement in the survival of the second-born twin when the latency period exceeded 2 days. When the outcomes were compared with
matched twin pregnancies in which the second twin was
delivered on the same or next calendar day, 56% of the delayed second twins survived to 1 year of age compared with
only 24% of the nondelayed second twins. When the first
twin delivered between 17 and 23 weeks, 32% of the delayed
second twins survived to 1 year of age, compared with only
7% of the nondelayed second twins. Similarly, when the first
twin delivered between 24 and 29 weeks, 89% of the delayed
second twins survived to 1 year of age, compared with 66% of
the nondelayed second twins. This study suggests that delayed interval delivery results in a significant improvement in
fetal outcome when the latency exceeds 2 days, which might
be attributable to the beneficial effects of steroids for fetal
lung maturity. Using the same database, a second group iden-
G.M. Graham III and S. Gaddipati
Table 1 Unfavorable Conditions for Delayed Interval Delivery
Gestational age <28 weeks
Monochorionic placentation
Chorioamnionitis
Placental abruption
PPROM of retaineed fetus(es)
Adanced cervical dilation
Nonreassuring fetal testing
tified 258 sets of twins in which the first twin was delivered
vaginally between 22 and 28 weeks and the second twin was
delivered at least 1 week later.43 In this series, there was only
a decrease in perinatal and infant mortality for those second
twins in which the first twin was delivered at 22 to 23 weeks
and when the delivery interval was between 1 and 3 weeks.
There was no benefit in outcome when the interval exceeded
3 weeks for any gestational age, or when the first twin was
delivered at 24 to 28 weeks and the interval exceeded 1 week.
It should be noted that, unlike the series that showed a benefit when the latency exceeded 2 days, this study defined a
delayed delivery as only those deliveries in which the interval
exceeded 1 week. For the cases in which the first twin delivered between 22 and 23 weeks, a delay of at least 1 week
likely resulted in the second twin reaching viability and possibly receiving steroids for fetal lung maturity. After 24
weeks, a delayed delivery less than 1 week includes those
pregnancies in which the second twin was retained for a
period that would allow for the beneficial effects of steroids.
Thus, it cannot be concluded that attempts at delayed interval delivery between 24 and 28 weeks for the administration
of steroids do not benefit the second twin. This study also
showed that the rates of small-for-gestational-age births in
the second twin increased with increasing delivery interval.
Although an increasing interval may be associated with impaired growth, other factors, such as multiple courses of steroids for fetal lung maturity, may have contributed to decreased fetal growth. Unfortunately, neither of these studies
was able to analyze the different management strategies or the
maternal risks associated with a delayed interval delivery.
Candidates for Delayed Interval Delivery
Attempts to delay delivery of the remaining fetuses following
the birth of the presenting fetus in a multiple gestation should
only be undertaken in the absence of any maternal or fetal
indications for delivery (Table 1). Consideration should be
given to the number of fetuses, the gestational age at the time
of delivery of the first fetus, placental chorionicity, evidence
of intrauterine infection, rupture of membranes of the retained fetus(es), placental abruption, and maternal and fetal
well-being.
Delayed delivery has been reported primarily in twin gestations; however, delayed delivery in higher-order multiples
has been attempted. In a 1999 review of interval deliveries in
multiple gestations, delayed delivery was attempted in 48
cases of twins, 12 cases of triplets, 2 cases of quadruplets, and
a single case of quintuplets.44 Despite the limited data on
higher-order multiples, attempts to delay delivery are reason-
Complications unique to multiple gestations
able in the absence of contraindications irrespective of the
starting number of fetuses.
The gestational age at the time of delivery of the first fetus
should be at least 16 to 18 weeks before prolonged interval
delivery is considered.39,40,45 In general, delayed delivery is
not recommended beyond 28 weeks, as the risks of prolonging the pregnancy may not outweigh the potential benefits.40,45,46 Therefore, candidates for interval delivery are
those who deliver the first fetus late in the second trimester or
early in the third trimester.
It has also been recommended that delayed delivery be
attempted only in multiples where each fetus has its own
placenta.39,40 The concern is that the shared placental circulation in a monochorionic twin gestation might predispose
the retained twin to neurological injury due to hypotensive
ischemia at the time of delivery.27 However, normal neurologic development has been reported in the surviving cotwin
of a monochorionic– diamniotic after delayed delivery.45 It is
possible that umbilical cord ligation at the time of delivery of
the first twin of a monochorionic pair might prevent the
hemodynamic changes that are believed to cause neurological injury in the cotwin. Even with immediate umbilical cord
ligation, patients and their families should be counseled
about the potential risk of neurological injury to the retained
twin in a monochorionic pregnancy. Although delayed delivery is reasonable to offer patients with previable delivery of a
monochorionic twin, the benefits of delayed delivery beyond
24 weeks are uncertain.
One of the most common reasons for discontinuing attempts at delayed delivery in multiple gestations is chorioamnionitis, which complicates approximately 36% of cases.47 Although there have been successful outcomes in rare cases in
which chorioamnionitis was treated with antibiotics, maternal sepsis complicates approximately 5% of cases of attempted delayed delivery.47 Despite isolated case reports of
successful interval deliveries when chorioamnionitis is suspected, such a strategy cannot be recommended given the
risks of both fetal and maternal morbidity and mortality.
Delayed delivery following PPROM in the retained fetus(es) is controversial. In a series of 8 cases complicated by
PPROM before 24 weeks’ gestation, aggressive management
to prolong the pregnancies resulted in a mean interval time of
48 days, with a range of 8 to 114 days.39 Management included the use of broad-spectrum antibiotics, high cord ligation after birth of the first fetus, both prophylactic and therapeutic tocolysis, and cerclage placement. With this
approach, 6 fetuses in 5 of the 8 pregnancies survived. An
addendum to this series included 3 additional patients who
were enrolled before publication who had less favorable results. No significant maternal morbidity was reported. Because of the mixed results in this series, further evaluation of
aggressive attempts to delay delivery in cases of PPROM in
the retained fetus(es) is needed before such a strategy can be
recommended.
Approach to Delayed Interval Delivery
If a delayed delivery is attempted, it is important to obtain
detailed informed consent from the parents. Counseling
289
should include a discussion of the benefits of a successfully
prolonged pregnancy, specifically that even modest intervals
during critical gestational ages can lead to a significant decrease in neonatal morbidity and mortality. However, patients should also be informed of the risk of delivering a
periviable baby after a relatively short interval with severe
morbidity related to prematurity, instead of delivering a
previable fetus that would not survive. Once informed consent is obtained, consideration should be given to the use of
steroids for fetal lung maturity, prophylactic antibiotics, tocolysis, cerclage, and inpatient management. If not documented previously, a detailed anatomic survey of the remaining fetus(es) is warranted as this may influence a family’s
decision to pursue aggressive management. In addition, aggressive attempts to prolong pregnancy should not be undertaken in cases of placental abruption, preeclampsia, chorioamnionitis, or nonreassuring fetal testing.
Ideally, candidates for delayed interval delivery should be
identified before the first fetus is born to allow appropriate
time for counseling and preparing a management strategy.39
After delivery of the presenting fetus, the umbilical cord
should be ligated with an absorbable suture placed as high as
possible inside the cervix. In women with a pregnancy in
each horn of a didelphys uterus, the placenta can be successfully removed after delivery of one twin, leaving the remaining twin and placenta undisturbed. Although the benefits of
steroids for fetal lung maturity have not been specifically
studied in multiple gestations, they are recommended for
patients at risk of preterm delivery between 24 and 34 weeks
of gestation with intact membranes, or between 24 and 32
weeks of gestation for patients with ruptured membranes.48
Similar guidelines should be applied to cases of delayed interval delivery in multiple gestations. Patients having had a
previable delivery should receive a single course of steroids
once the retained fetus(es) reaches 24 weeks of gestation. The
use of prophylactic antibiotics in these cases is controversial.
The rationale is to prevent ascending infection, thereby prolonging the pregnancy for the remaining fetus(es). Before
antibiotic prophylaxis is initiated, it is important to exclude
chorionamnionitis in the remaining fetus(es). If there is any
uncertainty about intrauterine infection, an amniocentesis
should be considered. Although the data are limited, routine
cultures of the vagina and cervix should be obtained. If prophylactic antibiotics are used, they should be broad-spectrum, such as ampicillin-sulbactam and metronidazole, to
cover the wide variety of bacteria that have been isolated from
the cervix, placenta, and amniotic fluid in cases of delayed
interval delivery. Since the benefits of prophylactic antibiotics in cases of delayed interval delivery are uncertain, a short
course of broad-spectrum antibiotics in the absence of infection is reasonable. Similarly, the role of tocolysis in delayed
interval deliveries is uncertain. There is enormous variation
in the literature regarding the choice of tocolytic, when tocolysis was started, and the length of time patients were treated.
Indomethacin may mask the clinical signs of chorioamnionitis and, therefore, is not the ideal choice when tocolysis is
used in cases of delayed interval delivery. Although no single
strategy has proven to be beneficial, it is reasonable to use
290
short-term tocolysis after delivery of the first fetus and avoid
the use of prolonged tocolytic therapy in most cases.
The benefit of cerclage placement in multifetal pregnancies
after delivery of one fetus is controversial. It has been suggested that a cerclage will close the cervix and decrease the
risk of an ascending infection. Another potential benefit of a
cerclage is that it adds stability to the cervix and support for
the remaining fetus(es), particularly if the cervix remains dilated after delivery of the first fetus. In contrast, others have
argued that placement of a cerclage may increase the risk of
initiating labor and chorioamnionitis. In a review of the literature, immediate cervical cerclage placement after the first
delivery was associated with a significantly longer interdelivery interval, 25 versus 8 days, without increasing the risk of
intrauterine infection.47 If a cerclage is considered, it is recommended that it be done soon after delivery of the first
fetus, as more favorable outcomes have been observed when
the cerclage is placed within 2 hours.46 While most cerclages
are performed using the McDonald technique, a two-cerclage
technique using both a Shirodkar and McDonald cerclage
may be employed to support the entire length of the cervix.49
Regardless of the elapsed time from delivery of the first fetus
or the technique used, it is important that uterine contractions have ceased, placental abruption and infection have
been excluded, and the well-being of the retained fetus(es)
and mother have been confirmed before a cerclage is attempted.
Whether patients attempting a delayed delivery require
hospitalization until the remaining fetus(es) has been delivered is uncertain. Advantages of outpatient management are
a more familiar and comfortable environment for the patient
and an overall reduction in hospital costs. All patients who
have delivered one fetus of a multiple gestation should be
hospitalized for an initial period of observation to monitor for
any evidence of preterm labor, chorioamnionitis, nonreassuring fetal status, or placental abruption. Fetal assessment of
the remaining fetus(es) will vary depending on gestational
age, but may include intermittent heart rate auscultation,
nonstress tests, or biophysical profiles. Fetal growth should
be followed closely by ultrasound given the risk of a smallfor-gestational-age birth in the retained twin.43 An individualized plan based on gestational age, degree of cervical dilation, compliance with modified bed rest, and social support
should be considered before outpatient management is pursued.
Patients who are candidates for an attempt at delayed interval delivery should be carefully selected and counseled
about the risks and benefits of this approach. Based on the
current literature, it seems reasonable to counsel them that in
the absence of any maternal or fetal indications for delivery,
attempts to delay delivery of a previable fetus might result in
a more favorable outcome for the retained fetus(es). And, that
delaying delivery between 24 to 28 weeks’ gestation for at
least 2 days to complete a course of steroids for fetal lung
maturity might also result in an improved outcome for the
retained fetus(es). However, the advantage of extending the
interval beyond 1 week at this gestational age is less certain.
Patients need to be aware that there are risks of maternal
G.M. Graham III and S. Gaddipati
Table 2 Ultrasound Criteria for Confirming Monoamniotic
Twins
One placenta
Both fetuses with same sex
No dividing amniotic membrane should be visualized
Each fetus must have adequate amniotic fluid surrounding
itself
Both fetuses must be able to move freely within the
uterine cavity
infection and delivering a baby with serious neurological
morbidity when a delayed interval delivery is attempted. At
the present time, the optimal management of a delayed interval delivery is not known, but broad-spectrum antibiotics,
tocolysis, and immediate cerclage is a reasonable strategy.
Importantly, the management of multiple gestations following the preterm delivery of one fetus must be individualized
according to the condition of the mother, the remaining fetus(es), and the wishes of the parents.
Monoamniotic Twins
Monoamniotic twins arise when the blastocyst splits between
day 8 and day 13 postfertilization, after the establishment of
the chorionic plate and amniotic sac. Monoamniotic twins
occur in approximately 1% of all monozygotic twin pregnancies. The literature points to a predominance of female infants. In addition to the other complications that can occur in
monochorionic gestations, monoamniotic twins are at elevated risk for fetal death due to cord entanglement. Because
monoamniotic twins are rare, reports in the literature are
limited to case reports, case series, and single-institution experiences over several decades, with more recent articles focusing on multicenter collection of cases or summation of
cases from the literature during the most recent era of advanced neonatal care.
Diagnosis of Monoamniotic Twins
Correct diagnosis is crucial with respect to appropriate counseling and proposed management. Before imaging modalities, the diagnosis was made postnatally, and occasionally
during the intrapartum period. Rodis and colleagues listed
several ultrasound criteria that should be satisfied to diagnose monoamnionicity in utero50 (Table 2). Although ultrasound technology and operator experience have improved to
the point that chorionicity and amnionicity can be correctly
predicted in virtually all cases during the first trimester, the
positive predictive rates are less later in pregnancy.51-57 The
presence of a single yolk sac can significantly aid in early first
trimester determination of amnionicity, and raises the suspicion for monoamniotic twins, as this structure can usually be
seen before visualization of a dividing amnion.58,59 The detection of cord entanglement, especially with color Doppler
and three-dimensional imaging also improves the accuracy of
antenatal diagnosis.60-67 Other methods described in the literature to determine amnionicity include sequential amniocentesis with injection of dye near one fetus, and repeat am-
Complications unique to multiple gestations
niocentesis at the opposite quadrant of the uterus to assess for
diffusion of dye, intraamniotic injection of air, creating microbubbles which act as an ultrasound contrast medium, and
amniography, utilizing radiopaque dyes followed by flat
plate x-rays or CT to assess for diffusion of the dye, or ingestion of dye by both fetuses. Although MRI and fetoscopy have
been utilized for diagnostic purposes in other fetal conditions, there are no articles describing their use for making the
diagnosis of monoamniotic twins.56,68-72 It is interesting to
note that twin–twin transfusion syndrome is reported as occurring rarely in monoamniotic gestations. This may be due
to an increase in numbers of all types of vascular connections
present in the monoamniotic placenta when compared with
the monochorionic diamniotic placenta.73-75 For a more thorough review of the twin–twin transfusion syndrome, the
reader is referred to the chapter by Drs. Harkness and
Crombleholme.
Management of Monoamniotic Twins
Based on older literature, fetal mortality rates associated with
monoamniotic twins have been reported to range from 30%
to 70%.76-79 Although all of these reports are retrospective,
there is a trend noted toward improved outcome over time.
Carr and colleagues reported their experience with 24 sets of
monoamniotic twins from 1967 to 1988. Although double
survival occurred in only 46% of cases, they noted no intrauterine death after 30 weeks’ gestation.80 Similarly, Tessen
and colleagues reported on 20 sets of monoamniotic twins
from 1961 to1989, noting a 65% double survival rate and no
stillbirths after 32 weeks’ gestation.81 One theory suggested
that, at a relatively late gestational age, movement of the
fetuses was restricted thus conferring a protective effect.
However, Tessen and colleagues noted after submission of
their article a double death at 35 weeks, again casting doubt
on optimal management. Rodis and colleagues reported on a
group of 13 sets of monoamniotic twins from 1986 to 1996.
With accurate prenatal diagnosis, serial sonography, and antenatal testing (9 of the 13 underwent daily nonstress tests),
double perinatal survival occurred in 92%.82 Similar reports
summarizing management of small case series (⬍34 sets of
monoamniotic twins per article) from the late 1980s to early
2000 cited perinatal survival rates from 60% to 98% (excluding abnormal fetuses).61,83-86 More recently, Roqué and colleagues summarized the outcomes of 133 monoamniotic sets
of twins from 1990 to 2002. Of note, perinatal mortality in
infants without anomalies was 18%, with 7% versus 21.6%
mortality rates for those with and without an antenatal diagnosis of cord entanglement. Also noted was a perinatal death
rate of 10.2% for pregnancies that continued beyond 32
weeks. With respect to morbidity, 25% of the surviving twins
after demise of the cotwin had evidence of neurological injury. Within this series, fetuses with anomalies were noted to
have a 43% perinatal mortality rate. Heyborne and colleagues
collected 96 monoamniotic sets from 1993 to 2003, summarizing outcome during a period reflecting contemporary neonatal intensive care unit (NICU) care and greater use of antenatal steroids for fetal benefit. The perinatal death rate
291
excluding lethal anomalies was 12.6%. A subanalysis of 87
sets of twins that continued after 24 weeks’ gestation compared twins that were either electively admitted for management with those that required an indicated admission. Elective admission patients underwent nonstress testing 1 to 3
times daily, whereas outpatient testing was performed 1 to 3
times weekly. No fetal deaths were noted in the 43 sets that
were electively admitted, whereas a 14.8% (13/88) death rate
was noted for the indicated admission group, with the latest
death occurring at 33 weeks’ gestation.73
Antepartum Management
of Monoamniotic Twins
The occurrence of cord entanglement resulting in compression and occlusion is clearly the significant contributor to
morbidity and mortality. Although the literature does not
give clear recommendations, smaller case series describe reserving inpatient management only when indicated.83,85,86
On the other hand, the larger series have led investigators to
recommend elective inpatient management in the hopes of
providing rapid response to nonreassuring fetal testing.73,82
At our institutions, admission for daily testing is recommended at whatever gestational age the woman would desire
intervention for nonreassuring fetal testing, usually at 26
weeks’ gestation.
Several investigators have reported and/or incorporated
the practice of medical amnioreduction by use of sulindac, a
nonsteroidal antiinflammatory drug known to decrease fetal
urine output with minimal adverse effect on the ductus arteriosus. Encouraged by the hypothesis that limiting movement within the uterine cavity may decrease cord compression and fetal death, Peek and colleagues reported 3 sets of
monoamniotic twins where fetal lie did not change after administration of daily sulindac starting between 24 to 27
weeks’ gestation, and all infants were delivered with good
outcomes.88 Overton and colleagues also reported successful
use of sulindac starting at 20 weeks’ gestation in 2 cases, and
Pasquini and colleagues successfully utilized it in 12 sets.
However, Sebire and colleagues reported that, in 2 sets of
twins treated with sulindac, only 1 infant survived. Although
this does not prove a causal relationship, it is clear that sulindac does not prevent cord entanglement, and at this time
there are not enough data to recommend its routine
use.64,89,90
While nonstress testing has been used to monitor for cord
compression, biophysical profiles and Doppler ultrasound
have been utilized to assess the fetal well being of monoamniotic twins in addition to aiding in the diagnosis of cord
entanglement.84,89,90 Abuhamad and colleagues noted that
umbilical artery notching may suggest increased resistance to
flow, suggestive of constriction of the vessel lumens; in severe
narrowing, diastolic flow may be greatly reduced. The authors suggested that, although further study was needed, the
presence of umbilical artery notching may be useful in dictating further management.91
292
Timing of Delivery and Intrapartum
Management of Monoamniotic Twins
There is no clear consensus when to effect delivery. As NICUs
have continued to improve their care and provide better outcomes, there is growing evidence to suggest that delivery
effected at 32 weeks is reasonable.73,87,92 In their report, Roqué and colleagues looked at the percent perinatal loss per
number of fetuses entering each 2-week gestational interval.
There was a statistically significant increase in perinatal loss
rates of 5.8%, 11%, and 21.9% for intervals 30 to 32 weeks,
33 to 35 weeks, and 36 to 38 weeks, respectively. Although
serial antenatal steroid use for fetal benefit was practiced in
many of the cases managed during the 1990s, more recent
reports suggest that antenatal betamethasone treatment
should be used judiciously, with limitations to the number of
courses administered.93
The optimal mode of delivery is also unclear. Cord entanglement is nearly ubiquitous, and cases of transection of a
nuchal cord at delivery proved to be the cord of the second
twin, necessitating its rapid delivery. Although many of the
case series have a significant number of twins delivering vaginally, more recent reports recommend elective cesarean section to avoid emergent delivery, and inadvertent transaction
of the second twin’s umbilical cord. When vaginal delivery is
considered, the appropriate skilled personnel and equipment
must be available to rapidly expedite delivery, be it emergency cesarean, or internal podalic version and/or breech
extraction. At our institutions, elective cesarean delivery is
recommended between 32 and 34 weeks’ gestation, after administration of betamethasone for fetal benefit.
Conjoined Twins
Incidence of Conjoined Twins
Conjoined twinning is an extremely rare complication of
monozygotic twins that results from incomplete embryonic
division occurring between 13 and 15 days after conception.
Because conjoined twins develop after differentiation of the
chorion and amnion, all conjoined twins are monochorionic–
monoamniotic. Monochorionic–monoamniotic twins account for less than 1% of monozygotic twins, and conjoined
twins are even less common, occurring in approximately 1 in
50,000 to 100,000 births.94,95 Conjoined twinning is 3 times
more common in female fetuses than males. Conjoined twins
are classified based on the most prominent site of union
together with the suffix pagus, which means fixed. Ventral
unions occur 87% of the time and are classified as: cephalopagus (11%), thoracopagus (19%), omphalopagus (18%),
ischiopagus (11%), and parapagus (28%).96 Dorsal unions
occur in 13% of conjoined twins and are defined as: craniopagus (5%), rachiopagus (2%), and pygopagus (6%).96
Diagnosis of Conjoined Twins
The diagnosis of conjoined twins can be made by ultrasound
in the first trimester. At this early gestational age, the diagnosis should be suspected if the embryonic pole appears bifid.97
However, the diagnosis should be made with caution in the
G.M. Graham III and S. Gaddipati
first trimester and, when suspected, follow-up imaging
should be performed to confirm the diagnosis. Additional
sonographic features of conjoined twins that may be apparent in the first and second trimesters include an inability to
separate the fetal bodies and skin contours, lack of a separating membrane between the twins, the presence of more than
three vessels in the umbilical cord, heads remaining at the
same level and body plane, extremities in unusual proximity,
and failure of the fetuses to change their relative positions
over time.97,98 The evaluation of conjoined twins should include a detailed ultrasound examination, including a fetal
echocardiogram, at 18 to 20 weeks to determine the extent of
shared organs and to exclude additional anomalies. Associated anomalies, even in organs unrelated to the conjoining,
are not uncommon.99 Further information may be gained by
MRI evaluation.100,101 A diagnosis of the anatomy of shared
organs and the presence of additional malformations is essential for counseling families regarding outcome and planning postnatal surgical separation.99 Because chromosomal
abnormalities are rare in conjoined twins, karyotyping is generally not indicated.99
Management of Conjoined Twins
If the diagnosis of conjoined twins is made before viability,
the option of pregnancy termination should be discussed.
The prognosis of the fetuses can be based on the extent of
fusion and the presence of additional malformations. Separation is rarely successful when there is cardiac or cerebral
fusion.94 Additional malformations unrelated to the site of
conjoining may also adversely affect prognosis. If a family
elects to continue with the pregnancy, the objectives are to
maximize the chance of survival of the twins and to minimize
maternal morbidity. Serial ultrasounds may be useful to further define the shared anatomy and the effect on fetal development. Polyhydramnios, secondary to circulatory imbalance, is a common complication of conjoined twins that
affects as many as 50% of cases.102 Amnioreduction may be
necessary to decrease the risk of preterm labor or premature
rupture of membranes, and to minimize maternal discomfort
from an overdistended uterus. Elective cesarean delivery
should be strongly considered once lung maturity is documented. In cases where one twin has a very low likelihood of
survival and endangers the life of the cotwin, an EXIT procedure should be considered.99
Outcome of Conjoined Twins
Survival of conjoined twins depends largely on the site of
conjoining and the organs involved. In a series of 14 cases of
prenatally diagnosed conjoined twins, 28% of cases died in
utero, 54% died immediately after birth, and only 18% survived.99 Emergent surgical separation is performed in the
event that one twin dies, or if a life-threatening condition
exists in one of the twins that threatens the life of the
cotwin. In these cases, the survival rate is reported as 30%
to 50%.103-105 Elective separation, which usually occurs at 2
to 4 months of age, allows for stabilization of the twins,
confirmation of anatomic relationships, diagnosis of previ-
Complications unique to multiple gestations
ously unrecognized anomalies, and adequate planning of
surgery. Most series report a survival rate of 80% to 90% for
elective separation.103-105
Conclusion
The diagnosis and management of obstetrical complications
in a multiple gestation pose a number of unique challenges.
These complex clinical scenarios demand thorough counseling of the expectant parents, as well as care by physicians
with expertise in the management of multiple gestations.
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