MINISTRY OF HEALTH OF THE REPUBLIC OF UZBEKISTAN
THE TASHKENT MEDICAL AKADEMY
POSTDATES pregnancy and Premature birth
(The lecture text)
For students 4 courses medical and medico-pedagogical faculties
Lecturer PhD
Nigmatova G.M.
Tashkent – 2013
PURPOSE.
-Define post-term pregnancy, principles of diagnosis;
-Give an idea of induction of labor;
-Define miscarriage;
-Train management of pregnant women with miscarriage;
- To teach students to prevent complications.
PLAN
- To determine the diagnosis of post-term pregnancy, the differential diagnosis of
post-term pregnancy and prolonged pregnancy
-Tactics of pregnancy and childbirth,
- Complications of pregnancy and childbirth from the mother and the fetus,
- Signs of over-ripe fruit and newborn.
-Cause miscarriage, diagnosis and treatment and methods of delivery in premature
birth pregnancy
- Signs of prematurity, complications of the mother and fetus,
The duration of a normal pregnancy is 40 weeks, referred to as “term,” with
delivery occurring most often between 38 to 42 weeks. A term pregnancy is 280
days from the last menstrual period, or 266 days from conception. Pregnancies
lasting beyond 42 completed weeks are defined as postterm or postdates
pregnancies. Delivery occurs by the estimated due date in 50% of patients, and
within the following 2 weeks in 35 to 40% of patients. The incidence of postdates
delivery ranges from 3 to 12%, and is somewhat difficult to accurately ascertain
because of inaccurate assessment of gestational age in many patients.
The postterm fetus is at severalfold increased risk for perinatal morbidity and
mortality compared with the fetus delivered at term. Causes of this excess
morbidity and mortality are placental dysfunction with associated
oligohydramnios and fetal dysmaturity, fetal macrosomia, and meconium
aspiration.
Dysmature neonates occur in 20% of postdates pregnancies. At birth, nye
dysmature newborn appears wizen, having lost its subcutaneous tissue. The skin is
peeling, the nails long, and meconium staining is common. This infant is at risk for
hypoglycemia, heat instability, and meconium aspiration. The amniotic fluid
volume peaks at 36 to 37 weeks’ gestation and decreases to less than half by 42
weeks. Meconium passage increases as pregnancy progresses, with 25 to 30%
incidence in meconium-stained amniotic fluid postterm. Meconium-stained fluid
will be thicker in postdates neonates because of the decreased volume of amniotic
fluid.
The oligohydramnios and placental dysfunction causes an increased risk of
in utero death and intrapartum fetal distress. However, placental dysfunction is not
always the case, and prolonged pregnancy results in macrosomic infants in
approximately 25% of postterm pregnancies. These infants are at increased risk of
birth trauma.
Management of postterm pregnancy begins in early pregnancy with accurate
determination of gestational age. In any patient where dates are known or there is
a size-date discrepancy, an ultrasound examination is necessary. Once a patient
passes her due date, the risk of continuing the pregnancy is weighed against the
risk of labor induction. The fetus is usually monitored with an NST or CST
conducted once or twice a week, and an ultrasound examination is obtained to
assess amniotic fluid volume. The cervix is assessed at each prenatal visit for
signs of successful induction and, if favorable, labor is induced. If fetal status
deteriorates, the cervix can be “ripened” with the use of laminaria, thin rods of
seaweed that absorb water and enlarge, causing cervical dilatation, or with
prostaglandin preparations. Continuous fetal monitoring is necessary intrapartum
because of the higher risk of fetal distress. For vaginal delivery of a macrosomic
postterm infant, a shoulder dystocia can be anticipated.
Premature birth is the Childbirth which has come in term of pregnancy from 28th
till 37th weeks беременности. The weight of a fruit — the Account of perinatal
death rate is carried out 1000 from 22 weeks pregnancy with weight of a fruit 500
gr and more.
The etiology, патогенез On a share of prematurely born children is necessary 60–
70 % early neonatal смертности and 65–75 % of children's death rate,
мертворождаемость at premature birth are observed at 8-13 time more often, than
at the timely.
Risk factors of perinatal disease and death rate at premature birth являются term
gestation and weight of a fruit, feature of a current of premature birth. These
factors are wrong position and fruit prelying, including тазовое prelying, normally
or low located placenta, fast or prompt childbirth. Childbirth in the rage from 22nd
till 27th week is considered as the most dangerous. At this time the fruit is still too
small (its weight fluctuates within 500-1000 gram). The organism of such kid isn't
adapted for a normal food as doesn't acquire some substances containing in parent
milk. The prematurely born child is extremely susceptible to infections, but the
main danger to life of the baby during this period is insufficient development of
lungs. Till 27 weeks in a fruit organism the substance interfering falling off of air
cells isn't developed (vials in which there is air), therefore to breathe independently
such child almost in a condition. Physicians struggle for life of such children and in
many cases nurse them, but usually don't give any forecasts. More often premature
birth on term from 22 till 27 weeks happens are caused by muscular insufficiency
of a neck of a uterus and an infection.
More a good situation in which premature birth begins on 28-33 week. During this
moment fruit lungs already stop to be formed, but still remain weak. Appointment
to the future mum of the special preparations accelerating development of lungs of
a fruit, allows to cope with this problem.
With increase in term of pregnancy chances of the kid of a survival increase also
the child who was born after 34 weeks, has very favorable forecast.
Distinguish true (biological) postdates pregnancy and imaginary (chronological),
or the prolonged pregnancy. Truly переношенная pregnancy proceeds more than
10-14 days after expected term of sorts (290-294 days). The child is born with
dead-ripe stage signs, and its life is in danger. Usually in these cases there are
changes from a placenta.
The prolonged pregnancy proceeds more than 294 days and comes to an end with a
birth доношенного, functionally mature child without signs of dead-ripe stage and
danger to his life. Frequency postdates pregnancy makes 1,4-14 %, on the aрerage
8 %.
Postdates pregnancy means untimely (overdue) occurrence of patrimonial
activity, at its development infringements сократительной activity of a uterus that
conducts to increase in number of operative interventions, to pre-natal suffering of
a fruit and increase of perinatal death rate are often observed.
At the prolonged pregnancy to name more correct childbirth timely and at true
перенашивании - overdue childbirth by an overripe fruit.
Perenoshennaja pregnancy – an etiology and patogenesis
Perenoshennuju pregnancy to consider as the pathological phenomenon caused by
the certain reasons, depending on an organism condition as mothers, and a fruit
more correctly.
Prоmorbidnym background for regnancy transferred earlier children's infectious
diseases (a scarlet fever, a parotitis, German measles, etc.), playing a considerable
role in formation of reproductive system of the woman, and also extragenetal
diseases can be.
Postdates pregnancy is promoted by the infantility, the transferred abortions,
inflammatory diseases of an internal. Which cause changes in the nervouslymuscular device of a uterus and lead эндокринным to infringements. A known
role in postdates pregnancy infringements of a fatty exchange, mental traumas,
toxicoses of second half of pregnancy play эндокринные diseases. At first
pregnency (especially elderly) postdates meets more often, than at ripited
pregnency. The hereditary factor Matters also.
The main pathogenetic moments conducting to postdates of pregnancy, functional
shifts in the central nervous system, vegetative and endokrin infringements are.
The big role belongs to infringement of development of an estrogen, gestogens.
Corticosteroids, oxytocin, some fabric hormones (acetylcholine, catecholamines,
serotonin, kinins, a histamine, prostaglandins), enzymes and vitamins. Certain
value has also a placenta and fruit condition.
Infringements in fetoplasentar system are one of the reasons of late occurrence of
patrimonial activity and its anomalies. The fruit becomes overripe, its requirement
for oxygen increases, stability of the central nervous system to oxygen
insufficiency decreases, Simultaneously there are radical changes in a placenta.
At postdates pregnancy the requirement for oxygen at a fruit raises, and stability to
a hypoxemia decreases, changes arising in a placenta complicate delivery to a fruit
of necessary quantity of oxygen and other necessary substances. So the vicious
circle of pathological processes, characteristic for postdates pregnancy is created.
Postdates pregnancy – a clinical picture
The clinical picture postdates pregnancy is expressed pregnancy softly, diagnostics
causes difficulties. At true postdates pregnancy more than 41 week it is often
observed; absence of increase of weight of a body of the pregnant woman or its
decrease more than on 1 kg; reduction of a circle of a stomach by 5 10 sm that
decrease skin tourist's mountain is usually connected with quantity reduction
околоплодных waters; falling of weight of the body, caused secondary hipotrofia
postdates is more rare than a fruit; green coloring amnion waters, higher standing
of a bottom of a uterus; milk allocation, instead of a colostrum, strengthening or
easing of movements of a fruit that specifies in a hypoxemia of a fruit owing to
infringement of matochno-placentary blood circulation; frequency change. A
rhythm and a timbre of warm tones of a fruit; immaturity or an insufficient
maturity of a neck of a uterus; the large sizes of a fruit. Increase in density of bones
of a skull, narrowness of seams and fontanels.
The current of sorts at postdates pregnancy is characterized numerous by
complications; premature amnion waters, anomaly of patrimonial activity, long
sorts, a hypoxemia of a fruit and a patrimonial trauma. As a rule, the pre-natal
hypoxemia of a fruit at postdates is shown with the beginning of patrimonial
activity or after premature amnion waters that is connected with deterioration of
matochno-placentary blood circulation in connection with is functionalmorphological changes in a placenta. The hypoxemia is promoted by the lowered
function of adrenal glands of a fruit, sensitivity to oxygen insufficiency at the time
of delivery owing to the raised maturity of the central nervous system, fall ability
of a head to a configuration, the considerable sizes of a fruit. Frequent
infringements сократительной uterus activity; excitation or stimulation of
patrimonial activity, frequent operative interventions at the time of delivery.
Postdates pregnancy – the diagnosis
The diagnosis postdates pregnancy usually put on the basis of the anamnesis and
the data received at clinical, laboratory and tool methods of research. It is
necessary to estimate the general condition of the pregnant woman, a current of the
given pregnancy (toxicoses), to establish occurrence term menarhe, features of a
menstrual cycle, infantility presence, endokrin diseases, the transferred
inflammatory diseases of genitals, abortions, postdates pregnancy in the
anamnesis.
To begin with let's be defined with terms. Normal average pregnancy keeps within
wide enough borders: 40 weeks from the first day of last menstruation (or 38
weeks from the date of conception), plus-minus of 2 weeks. And as the majority of
women can't precisely remember day of conception it is accepted to be guided for
40 weeks.
Childbirth on 37-42nd week isn't considered early or overdue. Pregnancy which
lasts 42 and more weeks and comes to an end with a birth normal the child without
dead-ripe stage signs, is called as prolonged. It meets twice less often postdates.
Anyway it is not necessary to panic.
At each woman the top border of normal term of sorts. What it defines?
If the cycle monthly is more than 28 days (from the first day of one menstruation
till first day following) pregnancy is more than 40 weeks – is normal.
Thus, the more days in a cycle, the it is possible without fears longer. Women with
a cycle have less than 28 days 36-40 – week pregnancy – norm.
If the first trimester of pregnancy passed with any complications, there is a
probability of its prolongation without signs postdates. The child in this case as
though gathers additionally that has received less on early terms.
If in a sort at the future mum someone bore the child longer 40 weeks with some
share of probability it is possible to expect it and at it. There is hereditarily caused
biorhythm of pre-natal development of the child, so, and approach of sorts.
If the woman has allowed to itself installation to give birth, for example, when the
husband will return from business trip or the doctor leaves holiday, its organism
can be arranged under this condition.
But all the same there are also cases really postdates pregnancy. Such situation
usually demands fast родоразрешения, and patrimonial activity not to hurry up to
begin.
What brakes childbirth and unequivocally testifies about postdates?
Sharp decrease in volume amnion waters – the precondition of development of
weak patrimonial activity.
Absence of "forward waters» (so-called «a flat bubble», fitting a head of the kid)
brakes childbirth and slows down disclosing of a neck of a uterus.
The unripe neck of a uterus on term of 40 weeks speaks about the big shares of
probability postdates pregnancy.
Dense bones of a skull of the child, narrow seams and fontanels complicate second
period – it is required much more efforts from mum and the kid.
Absence in amnion waters of flakes сыровидной ( according to ultrasonic) says
greasings about dryness of a skin of the child that testifies to dead-ripe stage.
Signs of aging of a placenta which are easily defined on ultrasonic say that the
placenta any more doesn't cope with requirements of the growing child.
Muddy from meconi (intestinal allocation of the kid ( amnion waters (according to
ultrasonic) tell the first about oxygen starvation of the child.
What reasons underlie postdates pregnancy?
Medical aspect postdates. Physicians consider that in a basis postdates pregnancy
absence of "biological readiness» organism of mum to sorts lies. It occurs because
of infringement of functions of the central nervous system of mum and the child
and (or) regulating function of a placenta.
Immaturity of immune system of a fruit, deficiency of vitamins C, Р, Е and groups
In also promote postdates, as well as эндокринные diseases, infringements of a
fatty exchange, the abortions, some diseases of genitals, mental traumas.
Plays a role and a heredity: if at someone in relatives were postdates pregnancy,
there is a probability postdates. Clinical analyses of blood and amnion liquids can
confirm a hormonal disbalance and infringements of endocellular power processes.
But too strengthened medical control in itself too can tighten terms of sorts. Socalled «biological unavailability» to sorts in most cases – a consequence of those
rother problems and fears of mum. Therefore it is possible to stimulate childbirth
both medical, and psychological means.
Childbirth can not begin because of various fears of mum. For example, threat of
interruption of pregnancy quite often leads to that she starts to behave so that as
much as possible to lower all processes provoking an abortion or premature birth.
Such prenatal processes as strengthening of a tone of uterine muscles, fights, the
softening and smoothing of a neck of a uterus, connect in consciousness of the
woman with fear to lose the child.
To stimulate childbirth, include in the life all those actions which have been
excluded in danger: long walks, walking on a ladder, gymnastics, swimming. Don't
neglect intimate life. In a word, relax and prepare itself for sort
Unconscious fears before sorts – at all a rarity. Productively work with fears on
courses of antenatal preparation, individual consultations of the psychologist will
help also. If the future mum all pregnancy conducted very active way of life, and
shortly before sorts has relaxed and began to take pleasure, pregnancy can be
tightened.
All is good in time and before sorts normally to test not weariness from pregnancy.
Constant control over displays of coming nearer sorts can be too importunate. It
doesn't allow to sorts to begin in time.
Distract itself from expectation by planning and realization of any affairs. For
example, it is good to start to prepare a dowry for the child, to lead up to shine «a
patrimonial nest», every day long to walk or go on a visit.
Very often relatives hurry events and infect with the uneasiness of the future
parents. If excitement amplifies, not out of place will be consultations at the good
expert or a campaign on ultrasonic to define presence or absence of signs really
переношенной pregnancy. If they aren't found out (even on term of 41-42 weeks),
means, time still is.
The most unequivocal factor demanding fast intervention, - presence in
околоплодных waters mekonical suspensions (according to ultrasonic) and
deterioration of indicators of palpitation of the child. Then it is useful for mum
even to be frightened a little for the kid that childbirth has begun. Professional
medical supervision and, probably, medicamentous stimulation of the beginning of
sorts anyway is required.
Discuss a problem postdates on a family council with the spouse and other adult
members of a family. You can express the collected feelings and experiences in
such conversation, to learn about feelings of others.
Happens that the fear of the future father before sorts and occurrence of the child
creates at the woman sensation of uncertainty – especially if she has got used to be
charged by this confidence from the husband. Then sincere and confidential
conversation, and sometimes even finding-out of relations (with obligatory
reconciliation, certainly) will render desirable and long-awaited therapeutic effect.
DATE of SORTS is the core that excites the women bearing under heart of the
child. Each pregnant woman wants any definiteness. Only having learned about
approach from itself long-awaited pregnancy, the future mum wants to learn date
of prospective sorts. But how it correctly to make? Many women try to calculate
date of sorts by date of conception. Also do it not in absolutely correct way, adding
to prospective date of conception of 9 months for calculation of date of sorts. But
such way of definition of date of sorts by date of conception isn't absolutely true.
Pregnancy lasts not exactly 9 months, and 280 days (10 lunar months). As
correctly to define date of sorts by date of conception? Whether there are other
techniques of definition of date of sorts? What of them the most exact?
Definition of date of sorts by date of conception and to day of an ovulation.
Date of sorts by date of conception is defined simply enough. As it is known, the
female organism is capable to conception only in an ovulation – an exit mature
яйцеклетки from яичника. The female menstrual cycle lasts, on the average 28-35
days. And the ovulation occurs in the middle of a menstrual cycle. Knowing date
of the ovulation it is possible to predict date of sorts easily. Some women feel the
ovulation. During this period they feel pricking or aching sensations in the bottom
of a stomach, the quantity выделений from a vagina increases, the sexual
inclination amplifies, and at some even begin not strong smearing (кровянистые)
allocation from a vagina. The ovulation with accuracy is defined on ultrasonic. But
how to define date of sorts if precisely you do not know day of an ovulation? For
this purpose it is possible to calculate simply the middle of the menstrual cycle and
to add by this day 280 days. Thus, you will calculate approximate date of sorts by
date of conception. For example, if your menstrual cycle lasts 28 days the
ovulation occurs somewhere for 12-14 day of a cycle. Add to date of prospective
conception of 10 lunar months (280 days), and receive approximate date of sorts. If
to calculate date of sorts by date of sexual intercourse such variant is even more
reliable, especially, if sexual intercourse in last menstrual cycle was individual.
But, it is necessary to remember that conception date can not coincide with day of
sexual intercourse. Сперматозоиды can "live" in a female organism about several
days. That is, if unprotected sexual intercourse has occurred for 10th day of a cycle
the ovulation and conception could occur for 12-13 day. And to count date of sorts
it is necessary proceeding by date of conception, that is, since day of an ovulation
Definition of date of sorts, proceeding from date of last menstruation
Coming on consultation to the gynecologist, usually, the first that the doctor asks is
when there was last menstruation. Young inexperienced girls, in the majority, not
especially watch a regularity of the menstrual cycle and can't name exact date.
Others start to remember a date started and the menstruation terminations. Though
for definition of term of pregnancy and date of prospective sorts it is necessary for
doctor to know only day of the first day of your menstruation. From this day also it
is reckoned a menstrual cycle and its duration is calculated.
The most simple formula which gynecologists for definition of date of sorts use is
a formula of Negele. To calculate on it date of sorts, it is necessary to take away
from the first day of the menstrual cycle three months and to add seven days. For
example, your last monthly have begun on April, 3rd. We take away three months
– it turns out on January, 3rd. Now we add by January, 3rd of 7 days. It turns out
on January, 10th is and there is a prospective date of sorts.
But this method of definition of date of sorts no means always differs split-hair
accuracy. As it is calculated for definition of approximate date of sorts for women
at whom a menstrual cycle makes exactly 28 days. If it is longer, also date of sorts,
most likely, will come hardly later and on the contrary. It is connected by that at a
long menstrual cycle the ovulation occurs later, and at short before 12-14 days, to
calculation on which the given formula is deduced. At an irregular menstrual cycle
so in general ovulation date to define very difficult and to use this method for
definition of date of sorts it is considered wrong.
Definition of date of sorts by means of ultrasonic.
It is considered the most exact to define date of sorts by means of ultrasonic
research on early terms of pregnancy, till 12 weeks. Having passed ultrasonic on
very early terms, it is possible to learn term of the pregnancy with accuracy
literally about one day, and according to it to calculate approximate date of
conception and date of sorts.
Pregnancy term put on ultrasonic and on later terms of pregnancy, according to the
sizes a head and fruit extremities. But already it is impossible to take the
conclusion of such ultrasonic for a basis for definition of date of sorts as all
children develop in own way, individually. Some children in weight of 5 kg, and
others – 3 kg also are born. Both that and another is norm. But here only in the first
case to the woman on ultrasonic in the second and third trimester of pregnancy will
expose term on pair-three weeks more than the present and accordingly, date of
sorts will be exposed earlier. Childbirth, most likely, will begin later, and doctors,
and the woman will hurry events, thinking that pregnancy переношенная, and
prospective date of sorts already has passed. And on the contrary, at low, thin
parents are born children with the same constitution. And on ultrasonic to the
woman make the diagnosis «a pre-natal arrest of development of a fruit» or simply
put term of pregnancy less, than it is actually, thereby remove correctly put date of
sorts for later term.
Statement of approximate date of sorts by results of gynecologic survey.
The gynecologist spending manual survey of genitals of the woman, can define
pregnancy "to the touch". It is possible to put pregnancy term absolutely precisely,
beginning from 3-4 weeks. It is necessary to know that on later terms (it is more 12
weeks) to put exact term of pregnancy and to define approximate date of sorts it
will be almost impossible. The reason of it the same, as at ultrasonic carrying out
on late terms is that each child develops in own way, individually. So, on what the
gynecologist pays attention at survey carrying out? First of all is the size and the
uterus form. At pregnant women the uterus gets the spherical form (at not pregnant
healthy women a uterus of the pear-shaped form) and increases in sizes. More or
less skilled doctor-gynecologist puts term of pregnancy and approximate date of
sorts, proceeding from the sizes of a uterus.
Definition of date of sorts on later terms of pregnancy.
There are cases when it is difficult to define date of sorts by date of conception. In
such cases it is possible to use such checked up technique, as definition of date of
sorts by date of the first шевеления the kid.
The kid in a womb of mother starts to make the first movements early enough,
about 12 weeks. But the pregnant woman doesn't feel them, as the baby is still
absolutely small. шевеления первородящая the woman starts to feel the presents
on term of 20 weeks, повторнородящая – in 18 weeks. In such a manner that to
calculate date of sorts, in the first case by day of the first шевеления it is necessary
to add 20 weeks, in the second case – 22 weeks. Thus, we will receive almost exact
date of sorts. Many women tell that start to feel the first шевеления much more
before the put term – in 16, and even 14 weeks. Gynecologists usually don't
perceive seriously such statements, writing off ostensibly шевеления the kid on
intestines reductions. But such sensitive women nevertheless meet and, in their
case, definition of date of sorts by date of the first шевеления the kid will be
incorrect.
Somewhere from 14-16 weeks of pregnancy the gynecologist can precisely define
term of pregnancy and approximate date of sorts by means of ordinary survey (not
on a gynecologic armchair). To the touch it will define height of a bottom of a
uterus on the basis of what and it will be possible to judge term of pregnancy and
to calculate date of sorts not by date of conception. In 16 weeks the uterus bottom
is between a pubis and a navel, in 24 weeks – around a navel, in 28 weeks – on 4-6
sm above a navel etc. There is other technique definition of term of pregnancy and
date of sorts – measurement of a circle of a stomach. But it accuracy doesn't differ,
as all of us different and waist volume is primary at all of us too the different. At
the women, inclined to completeness, the stomach volume will be, anyway, more
than at the thin woman to whom have put precisely such date of sorts.
Measurement of length of a uterus much more информативнее for calculation of
date of forthcoming sorts.
Why date of sorts is called not exact, but only approximate?
Really, to calculate exact date of sorts it is not obviously possible even by date of
conception. The reasons of errors of calculation of date of sorts on conception, we
have considered in the beginning of this article. Concerning small percent of
women gives birth precisely in time, defined by the doctor the gynecologist.
Though say that pregnancy should last exactly 40 weeks, but in many cases it not
so. Date of sorts can come and in 38 weeks and it also isn't a pathology. At
многоплодной pregnancy childbirth practically always comes before the date
defined by the gynecologist. For date of sorts, is more exact on its approach, can
influence and some other factors, such as многоводие, a high pressure at the
pregnant woman, a diabetes etc.
The duration of a normal pregnancy is 40 weeks, referred to as “term,” with
delivery occurring most often between 38 to 42 weeks. A term pregnancy is 280
days from the last menstrual period, or 266 days from conception. Pregnancies
lasting beyond 42 completed weeks are defined as postterm or postdates
pregnancies. Delivery occurs by the estimated due date in 50% of patients, and
within the following 2 weeks in 35 to 40% of patients. The incidence of postdates
delivery ranges from 3 to 12%, and is somewhat difficult to accurately ascertain
because of inaccurate assessment of gestational age in many patients.
The postterm fetus is at severalfold increased risk for perinatal morbidity and
mortality compared with the fetus delivered at term. Causes of this excess
morbidity and mortality are placental dysfunction with associated
oligohydramnios and fetal dysmaturity, fetal macrosomia, and meconium
aspiration.
Dysmature neonates occur in 20% of postdates pregnancies. At birth, nye
dysmature newborn appears wizen, having lost its subcutaneous tissue. The skin is
peeling, the nails long, and meconium staining is common. This infant is at risk for
hypoglycemia, heat instability, and meconium aspiration. The amniotic fluid
volume peaks at 36 to 37 weeks’ gestation and decreases to less than half by 42
weeks. Meconium passage increases as pregnancy progresses, with 25 to 30%
incidence in meconium-stained amniotic fluid postterm. Meconium-stained fluid
will be thicker in postdates neonates because of the decreased volume of amniotic
fluid.
The oligohydramnios and placental dysfunction causes an increased risk of
in utero death and intrapartum fetal distress. However, placental dysfunction is not
always the case, and prolonged pregnancy results in macrosomic infants in
approximately 25% of postterm pregnancies. These infants are at increased risk of
birth trauma.
The management of postterm pregnancy begins in early pregnancy with accurate
determination of gestational age. In any patient where dates are known or there is
a size-date discrepancy, an ultrasound examination is necessary. Once a patient
passes her due date, the risk of continuing the pregnancy is weighed against the
risk of labor induction. The fetus is usually monitored with an NST or CST
conducted once or twice a week, and an ultrasound examination is obtained to
assess amniotic fluid volume. The cervix is assessed at each prenatal visit for
signs of successful induction and, if favorable, labor is induced. If fetal status
deteriorates, the cervix can be “ripened” with the use of laminaria, thin rods of
seaweed that absorb water and enlarge, causing cervical dilatation, or with
prostaglandin preparations. Continuous fetal monitoring is necessary intrapartum
because of the higher risk of fetal distress. For vaginal delivery of a macrosomic
postterm infant, a shoulder dystocia can be anticipated.
Preterm Birth
Despite widespread programs in preterm birth prevention and the introduction of
tocolytic agents, the preterm birth rate in the United States remains at 9%. These
births account for up to 75% of perinatal morbidity and mortality. Classically, a
premature infant is defined as an infant weighing less than 2500 g at birth; an
alternative definition is an infant born before 37 completed weeks of pregnancy. A
low birth weight infant weighs less than 2500 g at birth independent of
gestational age. A very low birth weight infant weighs less than 1500 g at birth.
Prospectively, gestational age is a better indicator of prematurity than birth weight
determined after delivery. Risk factors for preterm delivery are epidemiologic,
pregnancy-related, underlying maternal causes, and unknown factors (table 12-1).
TABLE 12-1
Factors Associated with Spontaneous Preterm Labor
Epidemiologic factors
Maternal age
Race
Socioeconomic status
Marital status
Antenatal care lacking or inadequate
Short interval between pregnancies
Pregnancy-related Factors
Multiple gestation
Polyhydramnios
Placenta previa
Placental abruption
Infection
Fetal growth retardation
Genetically abnormal fetus
Intrauterine fetal demise
Maternal Factors
Previous preterm birth
Maternal weight/weight gain
Smoking, alcohol, drug use
Psychological stress
Coitus
Chronic disease
Uterine animalies
Cervical incompetence
Trauma
Abdominal surgery
Unknown
The immediate causes of preterm birth in order of frequency are premature labor,
preterm premature rupture of the membranes (PROM), obstetrical or medical
complications, and fetal distress.
Premature labor, the most common cause of preterm birth, is defined as uterine
contractions causing cervical effacement and dilatation occurring before 37 weeks’
gestation. Prior to presenting in premature labor, many women complain of
spotting, an increase in vaginal discharge, crampy lower abdominal pain, or
pressure. When a patient presents with painful regular uterine contractions, prompt
assessment is necessary. A fetal heart rate (FHR) strip with uterine
tocodynamometric monitoring can assess fetal status and quantify the frequency
and duration of uterine contractions.
Infection can be present with intact membranes with no other signs or symptoms
except preterm labor. Therefore, an underlying infectious etiology for preterm
labor must be sought to establish the diagnosis and initiate appropriate therapy. An
elevated maternal temperature should be treated because it can lead to uterine
contractions. Vaginal infections (e.g., bacterial vaginosis or trichomonas) may be
indicative of intrauterine infections. Cervical cultures for gonorrhea, group B
streptococcus, and chlamydiae should be obtained. Signs and symptoms of
chorioamnionitis (inflammation of the chorion and amnion), a cause of preterm
labor that may be present with intact membranes and no other signs or symptoms
of infection other than preterm labor, should be sought. Intra-amniotic infection
can be present when bacteria are seen on Gram stain of unspun amniotic fluid,
amniotic fluid with a white blood cell count above 50 cells/mm³, or an amniotic
fluid glucose concentration of less than 14 mg/dl. Preterm labor is also associated
with urinary tract infections, however, antibiotic treatment significantly reduces
the chance of a preterm birth.
Management of the patient in premature labor should be dictated by the initial
cervical examination. The patient whose cervix is long and closed should be
observed over a period of time to assess whether contractions continue and
produce cervical change. However, the patient presenting with the cervix dilated 3
cm and with regular uterine contractions is best managed by beginning tocolytic
therapy immediately. She should be placed on bed rest in the left lateral decubitus
position, intravenously hydrated, and the cervix monitored by serial examinations.
An initial period of observation can distinguish the 40 to 50% of patients in
preterm labor who can be managed with only bed rest and intravenous hydration
from those patients who require pharmacological therapy.
The patient should undergo a complete medical and obstetrical evaluation and
full physical examination, since prolongation of pregnancy with tocolytic therapy
may be contraindicated. The pregnancy should not be continued for obstetric and
medical reasons, such as a fetal death or fetal malformation incompatible with life,
placental abruption, severe pregnancy-induced hypertension or eclampsia, placenta
previa with life-threatening bleeding, chorioamnionitis, severe fetal growth
retardation, or the presence of any maternal medical condition in which
prolongation of the pregnancy is unwarranted.
Some clinical situations involve balancing the relative risk of continuing the
pregnancy by instituting tocolytic therapy against the risk of preterm delivery.
Ideally, accurate assessment of gestational age of the fetus will be accomplished
in early pregnancy, but many preterm labor patients need ultrasound fetal age
assessment. Since there is a greater error in fetal age assessment in late pregnancy,
many clinicians advocate amniocentesis for lecithin:sphingomyelin (L/S) and
phosphatidylglycerol (PG) determination either prior to initiating tocolytic therapy
or shortly after therapy begins.
Patients who are candidates for tocolytic therapy are those whose uterine
contractions do not respond to hydration and decreased activity, whose
contractions cause observed cervical change, and who have no contraindications to
pregnancy prolongation or the use of tocolytic agents.
Tocolytic therapies most often used include β-sympatomimetics, magnesium
sulfate, prostaglandin synthetase inhibitors, and slow calcium channel antagonists
(Table 12-2). No agent has been found to be significantly better than any other, and
true premature labor is rarely prolonged more than a few days. With fetal
pulmonary immaturity, corticosteroids administered to the mother have been
found to reduce the incidence and severity of respiratory distress syndrome,
intraventricular hemorrhage, and necrotizing enterocolitis in the premature
neonate.
In cases of true preterm labor, outcome is best if delivery occurs in a tertiary
care center with the availability of neonatal intensive care. The premature fetus has
less reserves than a term fetus, mandating FHR monitoring and operative
intervention if a nonreassuring FHR hattern develops. Cesarian section is often
used to deliver the premature infant presenting as a breech and the very low birth
weight infant.