Amniotic fluid phospholipids and foetal lung maturation.

An analysis was made of samples of amniotic fluid from 82 pregnant women with normal pregnancies, ranging from 29 to 40 weeks of amenorrhoea. Lipid extraction was quantitative and individual phospholipids were isolated by two-dimensional chromatography. The lecithin/sphingomyelin ratio (L/S) increased significantly (t = 2.17; p less than 0.05) between 35 and 36 weeks of amenorrhoea (from 2.9 +/- 1.0 to 4.3 +/- 1.7). Phosphatidyl-glycerol (PG) was detected from 35 weeks of pregnancy, the time at which the incidence of amniotic samples with mature surfactant (L/S greater than or equal to 2.7 and presence of PG) was 9%; mature surfactant incidence increased to 55.5% at 36 weeks and 100% at 37 or more weeks. There was a good correlation between surfactant levels in amniotic fluid and new-born respiratory function.