The lecithin/sphingomyelin ratio in 132 insulin-dependent diabetic pregnancies.

A total of 228 determinations of L/S ratios were performed in 132 insulin-dependent diabetic pregnancies. A declining L/S ratio was observed in 6 per cent of the cases without adverse effects on the fetus. No significant difference in the percentage of mature L/S ratios by weeks of pregnancy was found in the different classes of diabetes. An immature L/S ratio was associated with a significant increase of low Apgar scores. At each stage of pregnancy, there was no significant difference in the percentage of mature L/S ratios according to the sex of the baby nor according to the presence or absence of polyhydramnios. Among the five infants with HMD two had a mature L/S ratio within 2 days of birth. This represents 3 per cent incidence of false-positive results. Despite this finding, we feel that the determination of L/S ratio is a useful advance in the management of diabetic pregnancies.