Lamellar body concentrations and the prediction of fetal pulmonary maturity.

Abstract

Amniotic fluid lamellar body concentration was quantified in pregnancy and compared with the lecithin/sphingomyelin ratio and phosphatidylglyceryl to predict fetal lung maturity. Amniotic fluid was obtained from 56 patients at various gestational ages (16 to 42 weeks) and quantified on a Coulter counter set for particle size used for platelets (2 to 20 fl). The lamellar body concentration best agreeing with a mature lecithin/sphingomyelin ratio of 2 and with phosphatidylglycerol was determined. The lamellar body concentration cutoff was compared with the lecithin/sphingomyelin ratio and phosphatidylglycerol as a predicator of fetal lung maturity. Lamellar body concentration increased exponentially with gestation (r = 0.70, p < 0.001), as did the lecithin/sphingomyelin ratio (r = 0.78, p < 0.001). The two tests correlated with each other linearly (r = 0.67, p < 0.001). The lamellar body concentration cutoff value that best agreed with both mature lecithin/sphingomyelin ratio and phosphatidylglycerol was 30,000/microliters (kappa-test 0.66 and 0.73, respectively). In 28 patients delivered within 72 hours the lamellar body concentration correctly predicted four cases of respiratory distress syndrome (100% sensitivity and specificity). This study confirms that lamellar body concentration is a reliable and practical assay and should be evaluated further, especially for use in a community hospital setting.