AMNIOTIC-FLUID INSULIN AND C-PEPTIDE LEVELS IN DIABETIC AND NONDIABETIC WOMEN DURING EARLY-PREGNANCY

Thanks to the widespread use of amniocentesis, glucose, insulin, and C peptide have often been measured in amniotic fluid (AF) during late g estation, but little is known about their concentrations during early pregnancy. To better understand early fetal p-cell function under norm al conditions and in the presence of maternal diabetes, we measured gl ucose, insulin, and C peptide in the AF collected during weeks 15-22 i n 77 healthy and 9 diabetic women undergoing amniocentesis for clinica l indications and compared the results with those obtained during late pregnancy (weeks 34-36). The AFC peptide concentration was higher in diabetic women (102 +/- 53 vs. 38 +/- 2 pmol/L), in the women with a f amily history of diabetes (41 +/- 6 vs. 35 +/- 2 pmol/L), after the 19 th week of gestation (46 +/- 5 vs. 35 +/- 2 pmol/L; in the presence of lower glucose concentrations), and in the presence of maternal plasma glucose levels greater than 5.56 mmol/L (42 +/- 3.5 us. 34 +/- 2 pmol /L). The comparison between early and late gestation showed decreasing glucose and increasing C peptide concentrations in both healthy and d iabetic women (in the latter, C peptide values were always 3 times hig her), whereas the insulin concentration was increased in late gestatio n only in diabetic women. The AFC peptide/insulin molar ratio increase d throughout pregnancy in both healthy (from 0.97 +/- 0.06 to 4.3 +/- 1.2) and diabetic (from 2.9 +/- 1.1 to 13.2 +/- 1.6) women. These para llel changes suggest that the fetal clearance and/or degradation of in sulin and C peptide may greatly change during both normal and diabetic gestation.