Premature Rupture of Membranes (PROM)
Rupture of membranes before onset of labor is considered premature. Diagnosis is clinical. Delivery is recommended when gestational age is ≥ 34 wk and is generally indicated for infection or fetal compromise regardless of gestational age.
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.
PROM can increase risk of intraventricular hemorrhage in neonates; intraventricular hemorrhage may result in neurodevelopmental disability (eg, cerebral palsy).
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.
Sterile speculum examination is done to verify PROM, estimate cervical dilation, collect amniotic fluid for fetal lung 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.
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.
PROM 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 ampicillin and erythromycin, followed by 5 days of oral amoxicillin and erythromycin) are given; they lengthen the latency period and reduce risk of neonatal morbidity.
In pregnancies of < 34 wk, corticosteroids should be given to accelerate fetal lung maturity (see Preterm Labor : Corticosteroids).
IV magnesium sulfate should be considered in pregnancies < 32 wk; in utero exposure to this drug appears to reduce the risk of severe neurologic dysfunction (eg, due to intraventricular hemorrhage), including cerebral palsy, in neonates.
Use of tocolytics (drugs that stop uterine contractions) to manage preterm PROM is controversial; their use must be determined case by case.
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 and antibiotics.
If pregnancies are < 34 wk, give corticosteroids to accelerate fetal lung maturity, and if pregnancies are < 32 wk, consider magnesium sulfate to reduce risk of severe neurologic dysfunction.