Amniotic fluid and fetal maturity.

The lecithin/sphingomyelin ratio in amniotic fluid is a method of predicting fetal lung maturity. The L/H ratios in certain high risk pregnancies are poorly correlated with the shake test. The L/S ratios in drug addiction methadone pregnancies and diabetic pregnancies do not have a high degree of correlation with normal L/S ratios after 36 weeks of gestation and are often low.