Fetal lung maturity in diabetic pregnancies: relation among amniotic fluid insulin, prolactin, and lecithin.

Insulin, prolactin, and lecithin phosphorus levels were measured in 97, 62, and 44 amniotic fluid samples from third trimester normal, gestational diabetic, and insulin-dependent diabetic patients, respectively. There was no difference in lecithin phosphorus concentration (index of fetal lung maturity) among the three groups. The amniotic fluid insulin level was significantly higher in insulin-dependent diabetic patients, whereas there was no difference in amniotic fluid prolactin levels among the groups. Correlations of amniotic fluid prolactin levels with both lecithin phosphorus and insulin levels were not statistically significant in any of the groups. This is probably because amniotic fluid prolactin is decidual, rather than fetal, in origin. Even though amniotic fluid insulin levels, which reflect fetal levels, were significantly higher in insulin-dependent diabetic patients, there was no difference in the amniotic fluid lecithin phosphorus concentration in diabetic pregnancies compared with that in normal pregnancies. Moreover, there was a positive, and not a negative, correlation between amniotic fluid insulin and amniotic fluid lecithin phosphorus levels in diabetic pregnancies. These results do not support the theory that fetal hyperinsulinemia results in delayed pulmonic maturation in diabetic pregnancies.