Premature Rupture of Membranes

INTRODUCTION

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Of neonatal morbidity and mortality, 85% is a result of prematurity. Preterm premature rupture of the membranes (PPROM) is associated with 30-40% of preterm deliveries, and is the leading identifiable cause of preterm delivery. The 3 most common risk factors for PPROM are smoking, previous preterm delivery, and vaginal bleeding at any time during the index pregnancy.

PROM (AT TERM)

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PROM is ROM prior to the onset of labor at or beyond 37 weeks of gestation. Incidence of PROM is approximately 10% of pregnancies. Patients with PROM may present with chief complaints of leaking fluid, vaginal discharge, vaginal bleeding, and pelvic pressure, but are not in labor. Labor is defined as regular, painful uterine contractions resulting in progressive cervical effacement or dilation. The diagnosis of PROM can be made by looking for pooling of fluid in the vagina or leakage of clear fluid from the cervix and ferning or arborization of this vaginal fluid when allowed to dry on a glass slide and viewed with a light microscope and/or Nitrazine paper, which turns blue when it comes into contact with the vaginal fluid. Blood contamination of the Nitrazine paper can invalidate the results. Avoid a digital cervical exam unless prompt or immediate delivery is expected. If the diagnosis still is in question, the amniotic fluid index (AFI) can be helpful. If doubt still exists, transabdominal instillation of
1 mL of indigo carmine dye in 9 mL of sterile saline into the amniotic cavity under ultrasound
guidance and observance for staining of a vaginal tampon or a sanitary pad should alleviate any question of ROM.

The natural history of PROM is that 90% of patients enter spontaneous labor within 24 hours. The major question about management of these patients is whether or not to allow them to enter labor spontaneously or to induce labor. In large part, the management of these patients depends on the patients' desires; however, the major maternal risk at this gestation is intrauterine infection. The risk of intrauterine infection increases with the duration of ROM. Evidence supports the idea that induction of labor, as opposed to expectant management, decreases the risk of chorioamnionitis without increasing the cesarean section rate.

Hannah et al studied 5041 women with PROM, who were randomly assigned to induction of labor with intravenous oxytocin or vaginal prostaglandin E₂ gel versus expectant management for as many as 4 days with induction of labor for complications. This study concluded that in women with PROM, induction of labor with oxytocin or prostaglandin E₂ gel and expectant management resulted in similar rates of cesarean section and neonatal infection. Induction with oxytocin, however, resulted in a lower risk of maternal infection (endometritis), when compared with expectant management. Additionally, the women in the study viewed induction of labor more favorably than expectant management.

A small study in the European literature from 1996 concluded that women with PROM at term who have an unfavorable cervical exam safely can be managed expectantly and that expectant management resulted in fewer operative vaginal deliveries. This prospective randomized trial enrolled a total of 154 patients. In addition, several prospective studies have reported that with an unfavorable cervix, expectant management decreased the cesarean section rate and length of labor without increasing infectious morbidity.

If a patient desires expectant management after being presented with the evidence and a recommendation by her caregiver, undertake this course in the hospital and not at home. In Hannah's subanalysis of the International Term PROM Study, 650 women were managed expectantly at home and 1017 were managed expectantly in the hospital. The conclusions of this analysis were that, "expectant management at home, rather than in a hospital, might increase the likelihood of some adverse outcomes (e.g. cesarean section rate, numbers of neonates admitted to the NICU for > 24 hours, neonatal sepsis)." An additional consideration to hospital management is what care to administer in the hospital. The safest course is complete bedrest with continuous fetal heart rate monitoring. Alternative management strategies would include intermittent monitoring with some ambulation, which would include bathroom privileges.

PPROM

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PPROM is far more complicated than PROM at term. Questions about in hospital versus home management, steroid administration, antibiotic prophylaxis, tocolytic use, risks for pulmonary hypoplasia, fetal surveillance, bed rest, and hydration may be dependent on gestational age and multiple comorbidities. Several important factors affecting neonatal outcome are gestational age at delivery, estimated fetal weight, presence or absence of infection, and whether or not a course of steroids has been completed. These concerns are addressed throughout the remainder of this chapter.

Reduced fetal heart rate variability is not a sensitive sign in preterm infants. If a patient is at more than 32 weeks of gestation and has documented fetal lung maturity, delivery is recommended. Finally, if a patient has reached 32-35 weeks gestation and has documented ROM, delivery in the absence of documented pulmonary maturity may be considered in institutions with a neonatal intensive care unit equipped to manage the complications of prematurity.

PPROM AND ANTIBIOTICS, CORTICOSTEROIDS, FETAL SURVEILLANCE, AND TOCOLYTICS

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If the decision to manage a patient expectantly has been made, the institution of broad-spectrum antibiotics is advantageous. Multiple trials have examined the advantages and disadvantages of using antibiotics and of choice of antibiotics. The use of antibiotics has been associated with prolongation of pregnancy and a reduction in infant and maternal morbidity. The summary of the available literature supports the use of ampicillin (2 g q6h) and erythromycin (250 mg q6h) intravenously for 48 hours, followed by oral amoxicillin (250 mg q8h) and erythromycin base (333 mg q8h) for 5 days, for a total of 7 days of antibiotics. An alternative would be ampicillin/sulbactam (3 g q6h) intravenously for 48 hours, followed by amoxicillin/clavulanate (250 mg q8h) orally for 5 days, for a total of 7 days of antibiotics. A broad-spectrum cephalosporin or clindamycin may be substituted in patients who are allergic to penicillin. Prolonged antibiotics offer no advantages and may promote the emergence of resistance, such as
ampicillin-resistant Escherichia coli.

Little controversy about who should receive steroids should exist. The Consensus Development Panel of the National Institutes of Health recommends corticosteroid use for women with PPROM prior to 30-32 weeks of gestation in the absence of clinical chorioamnionitis. The dose is betamethasone 12 mg intramuscularly every 24 hours, 2 doses. In the initial statement, an allowance also was made for dexamethasone, but a considerable amount of evidence has developed since then that favors betamethasone for many reasons. There is no evidence to support the use of subsequent courses of this therapy.

Perform antepartum fetal surveillance at least daily, which may consist of a nonstress test (NST) and AFI. No evidence supports one form of testing over another or any specific frequency.

Tocolytics may be used to prolong gestation long enough to complete a course of corticosteroids (betamethasone 12 mg IM q24h, 2 doses). Be absolutely certain that an intraamniotic infection is not present before beginning tocolytics.

Pelvic rest is of utmost importance, as the risk of ascending infection increases not only with the duration of ruptured membranes, but also with manipulation of the cervix. When examining the cervix, this should be done with a sterile speculum, and not digitally. Furthermore, there is no need for frequent cervical exams in a patient who is without complaints of regular uterine contractions, pelvic pressure, vaginal bleeding, or other signs and/or symptoms of labor. The one exception is in the patient who has advanced cervical dilation and/or a nonvertex presentation. These patients are at increased risk for umbilical cord prolapse, and may require more frequent cervical exams (sterile speculum) in order to assess if further cervical dilation has occurred. If the patient has advanced cervical dilation (that is enough dilation to allow an umbilical cord to prolapse), and/or a nonvertex presentation, continuous fetal heart rate monitoring may be necessary. In many instances of cord prolapse, the only sign maybe severe variable decelerations or a prolonged deceleration in the fetal heart rate. This would be difficult to diagnose with intermittent fetal heart rate monitoring.

PPROM IN THE SECOND TRIMESTER

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ROM prior to fetal viability poses some unique problems. From 1984-1995, 11 maternal and fetal outcomes in pregnancies with PPROM in the second trimester (13-26 wk) were reported on. The major maternal risk is infection, namely chorioamnionitis. The major morbidity in the fetus with mid trimester ROM is lethal pulmonary hypoplasia from prolonged, severe, early oligohydramnios.

Chorioamnionitis occurs in 30-60% of patients with second trimester PPROM. The risk of infection increases with duration of ROM and an AFI less than 2.0 cm. Frequent exams are necessary to ensure maternal safety. Patients need to be educated about the warning signs of intraamniotic infection and need to take their temperature 3 times a day at home. These patients do not need to be cared for in the hospital if no evidence of vaginal bleeding or infection exists. They may consider admission for inpatient management at 24 weeks, which currently is considered the point of viability at most institutions.

Pulmonary hypoplasia is the most serious fetal complication and can be lethal. The presence of severe (AFI <2.0 cm), prolonged (>14 d), and early (<25 wk at onset) oligohydramnios has been associated with a neonatal mortality rate greater than 90% in one study. In other studies, the gestational age at the time of PPROM carried the most significance when predicting pulmonary hypoplasia. In the human fetus, ROM during the canalicular stage (13-25 wk) carries the most dismal prognosis. The diagnosis of pulmonary hypoplasia is made at autopsy by weighing the lungs. Several schemes exist for predicting pulmonary hypoplasia antenatally using lung lengths and/or thoracic circumference ratios, but the functional capacity of the lung cannot be predicted, only the amount of tissue present.

SUMMARY

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Manage PROM at term according to the patient's wishes, the cervical exam, and the presence or absence of any comorbidities (eg, infection). Evidence to support induction of labor shortly after diagnosis of PROM exists, and this is the protocol at the author’s institution, with few exceptions.

PPROM is considerably more complicated, and requires a thorough evaluation for gestational age, fetal position, presence of infection, and fetal and maternal well-being. Decisions about management are affected by each of these variables.