Amniotic fluid lecithin/sphingomyelin ratio in pregnancy complicated by diabetes

The lecithin/sphingomyelin (L/S) ratio in the amniotic fluid of 57 patients attending an antenatal diabetic clinic was determined. The L/S ratio in Class A, B and C patients (White, 1965) showed a similar rise with gestation to nondiabetic patients; 89 per cent in this group had an L/S ratio above 2 : 1, but of these 27 per cent developed mild or moderate respiratory distress syndrome (RDS). In Class D, F and R diabetic patients there was a little correlation of the L/S ratio with gestational age and in this group 55 per cent of the infants developed some form of RDS. The value of measuring amniotic fluid L/S ratios in the diabetic pregnancy is questioned.