Amniotic fluid content of glucose, C-peptide and insulin in normal and diabetic pregnancies.

Glucose, C-peptide and insulin concentrations in amniotic fluid were measured in 63 women, 19 of whom had insulin-dependent diabetes. The amniotic fluid glucose concentration was higher in the diabetic (37.4 +/- 4.1) than in the normal women (19.4 +/- 5.1 mg/dl; P less than 0.01). The amniotic fluid insulin concentration was higher in diabetic than non diabetic women (15.9 +/- 3.1 versus 8.9 +/- 2.1 microU/ml; P less than 0.01). The C-peptide concentration was also higher in the amniotic fluid of diabetic women than normal (1.60 +/- 0.66 vs 0.26 +/- 0.15 nmol/l; P less than 0.001). The lecithin/sphingomyelin (L/S) ratio in the amniotic fluid was greater than 2 in 61 mothers; only two diabetic patients had an L/S ratio lower than 2. Five neonates of diabetic mothers were macrosomic and three of these were also hypoglycaemic. A negative correlation was observed in diabetic women between insulin and C-peptide concentrations in the amniotic fluid and Apgar score of the newborn infants both at 1 and 5 minutes; no correlation was found on the contrary with the amniotic glucose. In the prognostic evaluation of the fetus with a diabetic mother one must consider many parameters. Among these more consideration must be given to the levels of C-peptide and insulin in amniotic fluid than to glucose level.