Amniocentesis and the management of premature labor

Two applications of amniocentesis for the evaluation of the patient in idiopathic premature labor, fetal lung maturity testing, and detection of occult intraamniotic infection were evaluated in a review of 59 cases. Seven patients (12%) had positive amniotic fluid cultures despite the absence of clinical signs of infection. This group presented at earlier gestational ages (29 + 2.3 versus 32 + 2.0 weeks, P less than .005) and were more likely to rupture membranes while on tocolytic therapy (four of seven versus two of 52, P less than .001) than patients whose cultures were negative. All seven patients with a positive culture delivered within 48 hours of admission, whereas 44 of 52 patients with negative cultures delivered after 48 hours (P less than .001). Increase in maternal and neonatal morbidity seemed to be related primarily to a higher cesarean section rate and earlier gestational ages at delivery in this group. Lecithin/sphingomyelin ratio was predictive of fetal lung maturity as expected. More than one-half of patients greater than 33 weeks and one-third of patients at 31 to 32 weeks demonstrated fetal lung maturity. The authors conclude that amniocentesis is an important tool in evaluating patients in preterm labor, especially with respect to making appropriate management decisions regarding tocolytic and/or corticosteroid therapy.