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Rupture
of the membranes before onset of labor is considered premature;
it sometimes results in infection. Diagnosis is clinical. If fetal lungs
are immature and infection is absent, treatment is bed rest plus
delay of delivery with Mg sulfate and other tocolytic drugs as needed. If
fetal lungs are mature or if fetal compromise or infection is present, treatment
is expedited delivery (eg, by inducing labor).
Premature rupture of membranes (PROM) may occur at term or earlier (called preterm PROM). Preterm PROM predisposes to preterm delivery. PROM at any time increases risk of infection in the woman (chorioamnionitis), neonate (sepsis), or both; prolapse of the cord; and fetal complications, such as abnormal joint positioning and pulmonary hypoplasia, which may occur with PROM at < 24 wk. Group B streptococci are the most common cause of infection. Other organisms in the vagina may also cause infection.
The interval between PROM and onset of spontaneous labor (latent period) and delivery varies inversely with gestational age. At term, about 80% of women with PROM begin labor within 24 h; at 32 to 34 wk, mean latent period is about 4 days.
Symptoms,
Signs, and Diagnosis
Unless complications occur, the only symptom is leakage or a sudden gush of fluid from the vagina. Fever, heavy vaginal discharge, abdominal pain, and fetal tachycardia, particularly if out of proportion to maternal temperature, strongly suggest infection.
Sterile speculum examination is done to verify PROM, estimate cervical dilation, collect amniotic fluid for culture and fetal maturity tests, and obtain cervical cultures. Digital pelvic examination, particularly multiple examinations, increases risk of infection and is best avoided. Diagnosis is assumed if amniotic fluid appears to be escaping from the cervix or if the fetal vernix or meconium is visible. Other less accurate indicators include vaginal fluid that ferns when dried on a glass slide or turns Nitrazine paper blue (indicating alkalinity, and hence amniotic fluid—normal vaginal fluid is acidic). Ultrasonography showing oligohydramnios suggests the diagnosis. Nonstress testing is done at least twice/wk if expectant management is used. In many hospitals, fetal monitoring is done daily while women are hospitalized. When gestational age is < 37 wk or unclear, fetal lung maturity can be assessed by amniotic fluid tests (eg, lecithin/sphingomyelin ratio); the sample may be obtained from the vagina or by amniocentesis.
Treatment
Management requires balancing risk of infection when delivery is delayed with risks due to fetal immaturity when delivery is immediate. No one strategy is correct, but generally, delivery should be prompt when there are signs of fetal compromise or infection (eg, persistently nonreassuring fetal testing results, uterine tenderness plus fever); otherwise, delivery can be delayed for a variable period if fetal lungs are still immature or if labor could start spontaneously (ie, later in the pregnancy). Some clinicians routinely induce labor when gestational age is > 34 wk.
When expectant management is used, bed rest is mandatory, and BP and temperature must be measured ≥ 3 times/day. Antibiotics, usually ampicillin and erythromycin , are given for 7 days; they lengthen the latent period and reduce risk of neonatal sepsis. Corticosteroids should be given to accelerate fetal lung maturity (see below) in pregnancies < 32 wk. Their use between 32 and 34 wk is controversial. If labor begins or persists before lungs are mature, Mg sulfate (see Abnormalities of Pregnancy: Treatment) or another tocolytic (a drug that stops uterine contractions—see Preterm Labor, below) can be given. Use of tocolytics is also controversial.
Last full review/revision November 2005
Content last modified November 2005
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