Evaluation of amniotic fluid in preterm labor with intact membranes

Amniotic fluid was obtained from 35 pregnant women in preterm labor with intact membranes. Their gestational ages ranged from 24 to 34 weeks. Bacteria were detected in only 1 (3%) of the 35 amniotic fluid samples. The anaerobic culture grew Bacteroides corrodens and Fusobacterium nucleatum. The L/S ratio was greater than 4.0 in six patients (17%), 2.5-4.0 in two (6%) and less than 2.5 in 23 (66%); the quantity of fluid was inadequate for L/S analysis in four (11%). None of the 35 newborns developed evidence of infection in the neonatal period. Only two women (6%) were febrile postpartum, and none experienced a prolonged hospital stay. Seven (20%) of the infants developed respiratory distress syndrome. Five (14%) developed hyaline membrane disease, and two (6%) had transient tachypnea of the newborn. Intrauterine infection may play a lesser role in preterm labor with intact membranes than previously postulated. Amniocentesis may provide useful information for directing management by permitting one to assess fetal pulmonary maturity and the presence of meconium.