The Diagnosis of Intrauterine Infection in Women With Preterm Premature Rupture of the Membranes (PPROM)

Abstract

Intrauterine infection caused by ascending vaginal bacteria is a significant problem in patients with preterm premature rupture of the membranes (PPROM). In a study of PPROM that used amniocentesis and percutaneous umbilical cord blood sampling to determine the incidence of intrauterine and fetal infection, three groups of patients were identified: (1) those without signs of infection, (2) those with intraamniotic infection only (positive amniotic fluid cultures), and (3) those with fetal infection (positive umbilical cord blood cultures).1 Patients with PPROM who were without evidence of infection had much longer intervals to delivery. Numerous other studies have found that patients with positive amniotic fluid cultures have a much higher incidence of developing clinical chorioamnionitis, much shorter intervals to delivery, and also a much higher incidence of neonatal complications, such as sepsis, pneumonia, and necrotizing enterocolitis, and increased perinatal death.1-3 Microbial invasion of the amniotic cavity can be found in approximately 30% of women with PPROM. At least 55% of patients with PPROM have histologic signs of infection at delivery.4 Intrauterine infection with PPROM leads to significant maternal and neonatal morbidity and mortality. The current recommended treatment of patients with PPROM includes expectant management in the asymptomatic patient until 34 or 35 weeks or until fetal lung maturity is documented, at which time labor is induced. This delay in delivery is thought to decrease the risk of neonatal complications of prematurity but also may increase the risk of neonatal infection. Identification of an intrauterine infection at the earliest stages, before the development of clinical chorioamnionitis, possibly would prevent serious neonatal complications due to infection.

Clinical signs of chorioamnionitis may occur late in the course of intrauterine infection and are present in only 25% of patients who have histologic chorioamnionitis at delivery.5 Prediction of patients destined to become infected can be difficult, and clinical findings are not consistently helpful. For example, Goldstein et al6 found no difference in maternal temperature between groups with positive versus negative amniotic fluid cultures. Therefore, numerous laboratory tests have been used to identify asymptomatic intrauterine infection. In this review we will examine the most recent studies that have evaluated different testing methods for identifying asymptomatic intrauterine infection in patients with PPROM. These include tests of maternal blood and amniotic fluid and of fetal behavior that use nonstress testing and ultrasound evaluation. We will evaluate only data specific for women with PPROM and not data from patients with preterm labor with intact membranes. This article will not address studies that evaluated tests for clinical chorioamnionitis; there is no need for a test to diagnose an obvious symptomatic condition. We then will discuss recommendations for the use of current testing modalities in the treatment of patients with PPROM.