Amniotic fluid phospholipid profile as a predictor of fetal maturity in diabetic pregnancies

The phospholipids in amniotic fluid from diabetic pregnancies were compared with those in normal pregnancies. There was little difference in the lecithin/sphingomyelin (L/S) ratios on the basis of the gestational ages. However, in diabetic pregnancies, phosphatidylglycerol (PG) was absent or low, and phosphatidylinositol (PI) remained high even if the L/S ratio was greater than 2. The phosphatidylglycerol/phosphatidylinositol (PG/PI) ratio was expressed as a function of the L/S ratio. The PG/PI ratio was significantly lower in maternal diabetes. Respiratory distress syndrome (RDS) coincided with an L/S ratio of between 2.0 and 3.0 only when PG was absent. Infants of insulin-dependent diabetic mothers with a particularly low PG/PI ratio (less than 50% of the median) had higher relative birth weights and more often had hypoglycemia than those infants born to mothers with a high PG/PI ratio (greater than 200% of the median). The phospholipids of amniotic fluid correlate with fetal functional maturity and may reflect deviations of hormonal balance required for normal perinatal development.