Amniotic fluid C-peptide and phosphatidyl glycerol in diabetic pregnancy.

The concentrations of C-peptide and phosphatidylglycerol in the amniotic fluid were determined in 36 pregnant diabetic women. Twenty-one patients who were being treated with insulin for gestational diabetes as well as 15 patients who were insulin dependent were studied. All patients were subjected to a program of strict metabolic control, and amniocentesis was performed at gestational week 36-37. Phosphatidyl glycerol was present in the amniotic fluid in 15 cases and absent in 21. The mean concentration of C-peptide did not differ whether phosphatidyl glycerol was present or absent. (C-peptide: 0.56 +/- 0.06 and 0.43 +/- 0.05 nmol/l respectively). Although the mean value for amniotic fluid C-peptide in both groups was close to that in diabetic pregnancies with an uneventful neonatal outcome, it was significantly higher than that in non-diabetic pregnancies, indicating minor fetal hyperinsulinemia. The level of C-peptide in the amniotic fluid showed a correlation to the subsequent birthweight of the infant (r = 0.50; p less than 0.01). It is concluded that with rigorous metabolic control of the pregnant diabetic patient, the presence or absence of phosphatidyl glycerol, as an index of fetal lung maturity, is apparently not related to the level of C-peptide in the amniotic fluid.