Fatty acid composition of amniotic fluid lecithin and its relationship to amniotic fluid C-peptide in diabetic pregnancy.

Fatty acid composition in lecithin and C-peptide was analysed in amniotic fluid samples obtained from 28 normal and 24 insulin-treated diabetic women in the 34th to 39th week of pregnancy. The pattern of changes of fatty acid composition of amniotic fluid (AF) lecithin was essentially the same in pregnancies complicated by diabetes as in non-diabetic controls. However, at 36/37 weeks, the mean values for palmitoleic acid (16:1) were statistically higher in diabetic women (P less than 0.02), and the mean values for stearic acid (18:0) were higher for normals (P less than 0.02). The mean C-peptide value was more than twice as high (0.71 nmol/l) in the diabetic group than in the control group (P less than 0.01). The lecithin/sphingomyelin (L/S) and palmitic/stearic acid (P/S) ratios were equal in both groups. Neither in five diabetic patients with fetuses indicating marked hyperinsulinism (C-peptide greater than 1.0 nmol/l) nor in the remaining group of patients was there any relationship between C-peptide levels and the lecithin fatty acid composition.