Rupture of membranes before onset of labor is considered premature. Diagnosis is clinical. Delivery is sometimes indicated when gestational age is ≥ 34 wk or fetal lungs are mature and is generally indicated for infection or fetal compromise.

Premature rupture of membranes (PROM) may occur at term (≥ 37 wk) or earlier (called preterm PROM if < 37 wk). Preterm PROM predisposes to preterm delivery. PROM at any time increases risk of infection in the woman (chorioamnionitis), neonate (sepsis), or both, as well as risk of abnormal fetal presentation and abruptio placentae. Group B streptococci and Escherichia coli are common causes of infection. Other organisms in the vagina may also cause infection. Prolonged preterm PROM before viability (at < 24 wk) increases risk of limb deformities (eg, abnormal joint positioning) and pulmonary hypoplasia due to leakage of amniotic fluid (called Potter sequence or syndrome).

The interval between PROM and onset of spontaneous labor (latent period) and delivery varies inversely with gestational age. At term, > 90% of women with PROM begin labor within 24 h; at 32 to 34 wk, mean latency period is about 4 days.

Symptoms and Signs

Typically, unless complications occur, the only symptom is leakage or a sudden gush of fluid from the vagina. Fever, heavy or foul-smelling vaginal discharge, abdominal pain, and fetal tachycardia, particularly if out of proportion to maternal temperature, strongly suggest chorioamnionitis.

Diagnosis

• Vaginal pooling of amniotic fluid or visible vernix or meconium
• Evaluation of vaginal fluid showing ferning or alkalinity (blue color) on Nitrazine paper
• Sometimes ultrasonography showing oligohydramnios

Sterile speculum examination is done to verify PROM, estimate cervical dilation, collect amniotic fluid for fetal maturity tests, and obtain samples for cervical cultures. Digital pelvic examination, particularly multiple examinations, increases risk of infection and is best avoided unless imminent delivery is anticipated. Fetal position should be assessed. If subclinical intra-amniotic infection is a concern, amniocentesis (obtaining amniotic fluid using sterile technique) can confirm this infection.

Pearls & Pitfalls If premature rupture of membranes is suspected, avoid doing digital pelvic examinations unless delivery seems imminent.

Diagnosis is assumed if amniotic fluid appears to be escaping from the cervix or if 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. Nitrazine test results may be false positive if blood, semen, alkaline antiseptics, or urine contaminate the specimen or if the woman has bacterial vaginosis. Oligohydramnios, detected by ultrasonography, suggests the diagnosis.

If the diagnosis is questionable, indigo carmine dye can be instilled using ultrasound-guided amniocentesis. Appearance of the blue dye on a vaginal tampon or peripad confirms the diagnosis.

If the fetus is viable, women are typically admitted to the hospital for serial fetal assessment.

Treatment

• Delivery if there is fetal compromise, infection, gestational age > 34 wk, or fetal lung maturity
• Otherwise, pelvic rest, close monitoring, antibiotics, and sometimes corticosteroids

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, signs of fetal compromise or infection (eg, persistently nonreassuring fetal testing results, uterine tenderness plus fever) should prompt delivery. 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). Induction of labor is recommended when gestational age is > 34 wk. When appropriate management is unclear, amniotic fluid tests can be done to assess fetal lung maturity and thus guide management; the sample may be obtained from the vagina or by amniocentesis.

When expectant management is used, the woman's activity is limited to modified bed rest and complete pelvic rest. BP, heart rate, and temperature must be measured ≥ 3 times/day. Antibiotics (usually 48 h of IV ampicillinSome Trade Names
OMNIPEN
PRINCIPEN
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and erythromycinSome Trade Names
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ERYTHROCIN
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, followed by 5 days of oral amoxicillinSome Trade Names
AMOXIL
TRIMOX
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and erythromycinSome Trade Names
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) are given; they lengthen the latency period and reduce risk of neonatal morbidity. In pregnancies of < 32 wk, corticosteroids should be given to accelerate fetal lung maturity (see Abnormalities and Complications of Labor and Delivery: Treatment). Their use between 32 and 34 wk is controversial. Use of tocolytics (drugs that stop uterine contractions) to manage preterm PROM is controversial; their use must be determined case by case.

Key Points

• Assume that membranes are ruptured if amniotic fluid pools in the vagina or if vernix or meconium is visible.
• Less specific indicators of PROM are ferning of vaginal fluid, alkaline vaginal fluid (detected by Nitrazine paper), and oligohydramnios.
• Consider inducing delivery if there is fetal compromise, infection, or evidence of fetal lung maturity or if gestational age is > 34 wk.
• If delivery is not indicated, treat with bed rest, antibiotics, and, to accelerate fetal lung maturity, corticosteroids.

Last full review/revision March 2013 by Julie S. Moldenhauer, MD

Content last modified March 2013