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Neurologic Complications in Multiple Pregnancy – Is It Possible To Reduce the
Incidence? What Are the Implications for Practice?
M. D’Alton
New England Medical Center Hospital, Boston, U.S.A.
Abstract
Cerebral Palsy (CP) is a chronic non-progressive symptom complex with an
incidence of 1/500 births characterized by aberrant control of movement and posture.
Less than 15% of cases are thought to be secondary to birth asphyxia. Additional causes
of CP include low birth weight, prematurity, genetic predispositions, infection, and
multiple gestations.
In the United States, the incidence of twin and higher-order multiples has been
increasing since the late 1980s, and multi-fetal gestations now comprise 3% of all
pregnancies. Meanwhile, twins alone are thought to account for 5-10% of all CP cases.
Understanding why multiple gestations are prone to neurologic morbidity is paramount to
designing and implementing prevention strategies.
Causes of neurologic morbidity in multiple gestations include preterm delivery,
low birthweight, and conditions unique to twin pregnancy such as intrauterine fetal
demise (IUFD) of one twin and the Twin-to-Twin Transfusion Syndrome (TTTS). In
addition, monochorionic twins are susceptible to growth abnormalities including growth
discordancy and intrauterine growth retardation (IUGR) which can result in fetal
compromise as well as preterm delivery.
Prevention strategies for neurologic morbidity include early ultrasound diagnosis
of chorionicity, targeted anatomy scans, prenatal diagnosis, and genetic counseling.
Patients should be referred to specialists attuned to the problems unique to twins.
Multifetal reduction should be offered to triplets and above as it has been associated with
improved perinatal outcomes.
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Patients should be monitored for signs and symptoms of preterm labor. Recent
studies indicate that a cervical length of less than 2.5 cm has been associated with an
increased risk of delivery prior to 32 weeks, and that a positive fetal fibronectin at 28
weeks has also been associated with an increased risk of preterm delivery. Nonetheless,
no intervention has proven useful to prevent preterm labor. Both prophylactic cerclage
and prophylactic tocolysis have not improved outcomes in patients with multiple
gestations. Due to the risk of adverse maternal sequelae such as fluid overload, tocolysis
should be utilized only in cases of documented preterm labor. In any situation where
delivery is thought to occur between 24 and 34 weeks, it is recommended that antenatal
steroids be administered.
Frequent ultrasounds are suggested to identify growth abnormalities in both
dichorionic and monochorionic twins. Once weight discordancy or IUGR has been
diagnosed, antepartum surveillance should be initiated. IUFD in one monochorionic twin
is challenging since the exact pathophysiology of the neurologic morbidity associated
with this occurrence is unknown, making it difficult to prevent. Monochorionic twins at
risk for IUFD require intense fetal monitoring. Early delivery should be considered if
IUFD is thought to be imminent.
Patients with mulitifetal pregnancies discordant for structural and/or chromosomal
abnormalities should be counseled about their options including expectant management
or depending upon the gestational age at diagnoses and the severity of the anomaly either
termination or selective termination. New technologies including radio-ablative therapy
are being tested as safe options for selective termination in monochorionic pregnancies.
The management of Acardia remains controversial. The goal is maximizing the normal
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twin’s outcome. Expectant management with serial ultrasound is reasonable in many
cases. Several percutaneous procedures have been described and are still experimental for
cases of Acardia with poor prognostic indicators. At this point, the optimal management
for TTTS is unknown. A randomized prospective NIH trial is currently ongoing to
determine if serial amnioreduction versus laser ablation improves outcomes.
In summary, multiple gestations are increasing and these fetuses have significant
risk for neurologic morbidity. Multiple management strategies, including early and
frequent ultrasounds to determine chorionicity, to diagnosis abnormalities, and to follow
growth, are needed. Likewise, it is recommended that women be counseled about the
signs and symptoms of preterm labor. Pathophysiologic states unique to twins such as
anomaly discordancy, IUFD of one twin, monoamnionicty, Acardia, and TTTS should be
managed by specialists knowledgeable about these disease processes.