Amniotic fluid lecithin/sphingomyelin ratio in complicated pregnancies.

Amniotic fluid (AF) lecithin/sphingomyelin (L/S) rations were obtained in 223 pregnancies. Gestations complicated by maternal diabetes (71), vascular disease (50), and fetal growth retardation (47) were included. Elevated L/S ratios at 34 to 36 weeks' gestation were observed to accompany maternal vascular disease; higher rat;os were also related to fetal sex (female) and race (black). Declining L/S rations were observed in 14 of 35 diabetic patients studied serially (40 per cent) and were accompanied by increased perinatal morbidity and deaths. These data suggest an urgent need for further studies concerning the clinical usefulness of a serial decline in the L/S ration as a predictor of fetal compromise.