Amniotic fluid volumes and concentrations of C-peptide in diabetic pregnancies.

Amniotic fluid (AF) volumes were determined by sodium p-aminohippurate (PAH) dilution in a consecutive series of 24 diabetic women at 34-35 weeks gestation. AF and maternal venous blood samples were analysed for C-peptide immunoreactivity (CPR). When the patients were subgrouped according to the presence (n = 17) or absence (n = 8) of neonatal morbidity, AF volumes (1340 +/- 236 ml vs 807 4/- 130 ml; mean +/- SEM), AF concentrations of CPR (1.38 +/- 0.54 nmol/l vs 0.61 +/- 0.14 nmol/l) and maternal blood glucose levels (5.3 +/- 0.2 nmol/l vs 4.8 +/- 0.3 nmol/l) during the last trimester of pregnancy were not different. The total content of CPR was significantly (P less than 0.05) greater in pregnancies with neonatal complications (1.25 +/- 0.31 nmol/ compared with that in pregnancies without neonatal complications (0.54 +/- 0.18 nmol). AF volumes were significantly (P less than 0.02) larger in pregnancies where feeding problems occurred (1546 +/- 307 ml, n = 9) compared with that in pregnancies without such problems (957 +/- 188 ml, n = 16). These findings indicate an impact of fetal hyperinsulinism on the functional maturation of the fetus. When the patients were subgrouped according to the presence or absence of detectable maternal plasma CPR, i.e. greater than 0.05 nmol/l, and to insulin dependent and gestational diabetes no differences of AF volumes, AF concentrations of CPR or total AF contents of CPR were found.