Pulmonary surfactant and amniotic fluid insulin.

Immunoreactive insulin was measured in 66 amniotic fluid samples and the level compared to two indices of pulmonary surfactant activity, namely, lecithin sphingomyelin ratio and lecithin palmitic acid. An apparent inverse relation between lecithin and insulin was demonstrated after 34-35 weeks' gestation. These results tend to support the hypothesis that insulin can inhibit lecithin synthesis.