Amniotic fluid C-peptide and cortisol in normal and diabetic pregnancies and pregnancies accompanied by fetal growth retardation.

The interrelationship between amniotic fluid (AF) concentration and content (AF X conc) of C-peptide and cortisol was studied in four groups of women comprising 10 gestational and 16 type-I diabetics, 11 women with intrauterine growth retarded fetuses (IUGR), and 17 healthy control women. Mean AF volume was significantly greater (P less than 0.05) in the type-I diabetic group than in the control group. Both concentration and content of AF C-peptide was significantly higher in the type-I diabetic group than in the control group (P less than 0.05 and P less than 0.01, respectively). The corresponding values were significantly lower in mothers with IUGR fetuses compared to controls (P less than 0.05). AF cortisol content was significantly higher (P less than 0.05) in the gestational diabetic group compared to the control group; there were no other significant differences between the groups regarding the cortisol concentration or content. Both cortisol and C-peptide contents were significantly interrelated in both control women (r = 0.68, P less than 0.01) and women with gestational (r = 0.68, P less than 0.05) and type-I diabetes (r = 0.63, P less than 0.01). The C-peptide/cortisol ratio was lowest in the IUGR group and highest in the type-I diabetic group. The same ratio was intermediate and almost equal in the control and gestational diabetic group. Both C-peptide and cortisol concentrations were unrelated to AF volume as well as infant birthweight. C-peptide content was significantly correlated to birthweight percentile in type-I diabetic women (r = 0.61, P less than 0.05). No such correlation was found in the three other groups.