Lecithin/sphingomyelin ratio in pregnancies complicated by diabetes mellitus.

The amniotic fluid lecithin/sphingomyelin (L/S) ratio was determined in 182 pregnancies complicated by Classes B and C diabetes and in 28 patients with Classes D, F, and R diabetes. These data were retrospectively correlated with the occurrence of the respiratory distress syndrome (RDS) or hyaline membrane disease (HMD). Only four cases of RDS and two cases of HMD were observed in 200 patients with an L/S ratio of 2.0 or greater prior to delivery. This 3 per cent incidence of complications is no higher than that of the nondiabetic population in our institution. Seven of 10 neonates with an antenatal L/S ratio of 1.5 to 1.9 developed RDS. An L/S ratio of 2.0 or more appears to be reliable predictor of fetal pulmonary maturity even in pregnancies complicated by diabetes mellitus.