Amniotic fluid insulin and C-peptide as predictive markers for fetal macrosomia, birth injuries, and delivery complications?

BACKGROUND Gestational diabetes mellitus (GDM) occurs in 3-5% of all pregnancies. GDM increases both maternal and fetal risks, causes fetal macrosomia, and hence increases the rates of caesarean sections and delivery complications such as shoulder dystocia. An early predictive marker and consequent early treatment could be beneficial, so amniotic fluid insulin and C-peptide have been examined in several studies. Increased amniotic fluid insulin in early amniocentesis between the 14th and 20th gestational week predicted a later GDM. A potential direct association with fetal macrosomia remains to be determined. MATERIAL AND METHODS This retrospective study investigated amniotic fluid insulin/C-peptide from amniocenteses between 14 and 20 weeks of gestation in correlation with fetal birth weight, type of delivery, and complications. To focus on effects of fetal hyperinsulinism apart from therapeutic confounders, we included patients who did not participate in GDM screening. Insulin and C-peptide were measured in 144 samples of frozen amniotic fluid. Birth weight, type of delivery, complications, and birth injuries were noted. RESULTS Birth weights ranged from 760 g to 4410 g with a mean weight of 3424 g at an average of 40 weeks gestation. The mean amniotic fluid insulin was 4.36 U/ml and the mean C-peptide concentration was 0.076 ng/ml. There was no correlation between amniotic fluid insulin or C peptide and birth weight, type of delivery, complications, and birth injuries. CONCLUSIONS Amniotic fluid insulin and C-peptide are unsuitable as predictive marker for fetal macrosomia, type of delivery, complications, or birth injuries.