EVALUATION AND MANAGEMENT
Factors to be considered in the
management of the patient with PROM include the gestational age at the time of
rup-ture, assessment of fetal well-being, the presence of uter-ine
contractions, the likelihood of chorioamnionitis, the amount of amniotic fluid
around the fetus, and the degree of fetal maturity. These management factors,
together with the patient’s history, must be carefully evaluated for
information relevant to the diagnosis and approach. Abdominal examination
includes palpation of the uterus for tenderness and fundal height measurement
for evalu-ation of gestational age and fetal lie.
A sterile speculum examination is
performed to assess the likelihood of vaginal infection and to obtain cervical
or vaginal cultures for N. gonorrhoeae,β-hemolytic strepto-coccus, and Chlamydia trachomatis. The cervix is
visualized for its degree of dilation as well as for the presence of
free-flowing amniotic fluid. Fluid is obtained from the vaginal vault for
nitrazine and/or fern testing. Because of the risk of infection, digital examination should be kept to a
min-imum and is best avoided until the patient is in active labor.
Ultrasound examination can be
helpful in determining gestational age, verifying the fetal presentation, and
assess-ing the amount of amniotic fluid remaining within the uter-ine cavity.
It has been shown that labor and infection are less likely to occur when an
adequate volume of amniotic fluid remains within the uterus.
If PROM occurs at term (>=37 weeks of gestation),
spon-taneous labor will ensue in 90% of women within about 24 hours.
Awaiting
the onset of spontaneous labor for 12 to 24 hours is reasonable, unless there
are risk factors such as previous or concurrent vaginal infection (such as
Group B streptococcus) or multiple digital pelvic examinations.
However, with informed consent,
induction of labor at any time after presentation of a PROM at term is also
consid-ered appropriate. Information that the physician should share with the
patient as this decision is considered includes, in addition to the risk of
infection, that oxytocin administra-tion is associated with a decreased risk of
chorioamnionitis and endometritis, and that there appears to be a decrease in
the incidence of cesarean delivery in patients managed expectantly. Serial
evaluation for the development of intrauterine infection (fever, uterine
tenderness, and mater-nal and/or fetal tachycardia) and other complications of
PROM is requisite with expectant management, which, in most cases, should not
extend beyond 24 hours in term preg-nancy. When
the decision to deliver is made, group B streptococ-cal prophylaxis should be
given based on prior culture results or risk factors, if cultures have not been
previously performed.
The time from PROM to labor is
called the latencyperiod and is
inversely related to gestational age. Between28 weeks and term, about 50% of
patients go into labor within 24 hours and 80% within 1 week. Only 50% of
patients whose gestational age is 24 to 28 weeks go into labor within 1 week of
PROM.
Amniocentesis can be helpful in
assessing fetal lung maturity (FLM), but can be difficult in the setting of
PROM and oligohydramnios. In addition to tests of FLM, evalua-tion for
intra-amniotic infection (using the presence of bac-teria on Gram stain,
elevated WBC count, low glucose level, or a positive culture) can also be
performed. If there is suffi-cient volume, FLM tests can also be performed on
amniotic fluid obtained vaginally.
If there is strong clinical
suspicion for the presence of uterine infection, delivery should be effected as
soon as pos-sible, regardless of gestational age.
If the
evaluation suggests intrauterine infection, intravenous antibiotic therapy and
delivery are indicated, regardless of gestational age.
The antibiotic prescribed should
have a broad spectrum of coverage, because of the polymicrobial nature of the
infection. The effect of tocolysis to permit antibiotic and antenatal
corticosteroid administration in the patient with preterm PROM who is having
contractions has yet to be conclusively evaluated; therefore, specific
recom-mendations for or against tocolysis administration can-not be made.
If the
gestational age is thought to be in the transitional time of fetal maturity
(i.e., from 34 to 36 weeks), the management is variable, depending on
individual circumstances (Table 22.2).
Because of the increased risk of chorioamnionitis and because steroids are not recommended after 34 weeks to increase fetal maturity, delivery is recommended when PROM occurs at or beyond 34 weeks of gestation. If PROM occurs at 32 to 33 completed weeks of gestation, the risk of severe complications of prematurity is low if FLM is evident by amniotic fluid samples collected vaginally or by amnio-centesis. The efficacy of corticosteroid use at 32 to 33 weeks of ges-tation has not been specifically addressed for women with PROM, but is recommended by some experts.
If PROM occurs at 24 to 31
completed weeks of gesta-tion, patients should be cared for expectantly, if no
maternal or fetal contraindications exist, until 33 completed weeks of
gestation. Prophylaxis using antibiotics to prolong latency and a single course
of antenatal corticosteroids can help reduce the risks of infection and
gestational age-dependent neonatal morbidity. Patients are assessed carefully
on a daily basis for uterine tenderness as well as maternal or fetal
tachy-cardia. WBC counts may be obtained and compared with baseline, although
the maternal WBC count is again non-specific and can be affected by
glucocorticoid administra-tion. Intermittent ultrasound assessment helps to
determine amniotic fluid volumes, because leaking of fluid from the vagina may
cease and allow amniotic fluid to re-accumulate around the fetus. Daily fetal
movement monitoring by the mother can also be helpful to assess fetal
well-being. In the absence of sufficient amniotic fluid to buffer the umbilical
cord from external pressure, compression of the cord can lead to fetal heart
rate decelerations. If these are frequent and severe, there should be early and
expeditious delivery to avoid fetal compromise or death. Unfortunately, such an
umbilical cord accident often is unrecognized for a time, regardless of the
monitoring regimen instituted. Electronic fetal monitoring is used frequently
during the initial evalu-ation period to search for any fetal heart rate
decelerations, although the fetal cardiac control mechanisms are often
insufficiently developed in preterm fetuses to allow mean-ingful evaluation for
fetal heart rate variability and reactivity.
PROM at very early gestational
ages, such as before 20 to 22 weeks of gestation, presents additional problems.
Along with the risks of
prematurity and infection already discussed, the very premature fetus faces the
further haz-ards of pulmonary hypoplasia, skeletal malformations, and other
consequences of prolonged oligohydramnios. The relation of PROM with both of these
entities is both inter-esting and important. The inability of the fetus to move
freely within the amniotic sac can lead to skeletal contrac-tures, which can
become permanent deformities. For nor-mal fetal lung development to occur,
fetal breathing must occur. During intrauterine life, the fetus normally
inhales and exhales amniotic fluid, with the net movement out into the amniotic
fluid space. This adds substances generated in the respiratory tree to the
amniotic fluid pool, including the phospholipids that form the basis for many
of the fetal maturity tests. If rupture of fetal membranes occurs before 22
weeks of gestation, the lack of amniotic fluid interferes with respiratory
efforts and, thus, with sufficient pulmo-nary development. The result is a
failure of normal growth and differentiation of the respiratory tree and fetal
chest. If severe, pulmonary hypoplasia may occur, which leads to an inability
to maintain ventilation.
Women presenting with PROM before
potential viability should be counseled regarding the impact of imme-diate
delivery and the potential risks and benefits of expectant management.
Counseling should include a realistic appraisal of neonatal outcomes, including
the availability of obstetric monitoring and neonatal intensive care
facilities. Because of advances in perinatal care, mor-bidity and mortality
rates continue to decline. An attempt should be made to provide parents with
the most up-to-date information possible. Women with previable preterm PROM are
usually managed expectantly, either at home or in the hospital. Once the
pregnancy has reached viabil-ity, administration of antenatal corticosteroids
for fetal maturation is appropriate, given that early delivery remains likely.
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