Fetal pancreatic β-cell function in pregnancies complicated by maternal diabetes mellitus: Relationship to fetal acidemia and macrosomia

Our purpose was to investigate the relationship between fetal pancreatic beta-cell function and fetal acidemia and macrosomia in pregnancies complicated by maternal diabetes mellitus.A cross-sectional study at the Harris Birthright Research Centre for Fetal Medicine, London, was performed. In 32 pregnancies complicated by maternal diabetes mellitus cordocentesis was performed at 36 to 39 weeks' gestation for the measurement of umbilical venous blood pH, PO2, PCO2, lactate, and glucose concentration; plasma insulin immunoreactivity; and insulin/glucose ratio. A reference range for plasma insulin and insulin/glucose ratio was constructed by studying fetal blood samples from 80 women who did not have diabetes mellitus.Mean umbilical venous blood pH was significantly lower and plasma insulin immunoreactivity and insulin/glucose ratio were significantly higher than the appropriate normal mean for gestation. There were significant associations between (1) maternal and fetal blood glucose concentrations (r = 0.95, p0.0001), (2) fetal blood glucose and plasma insulin immunoreactivity (r = 0.57, p0.01), (3) fetal plasma insulin immunoreactivity and blood pH (r = -0.39, p0.05), and (4) fetal insulin/glucose ratio and degree of macrosomia (r = 0.76, p0.0001).Fetal pancreatic beta-cell hyperplasia is implicated in the pathogenesis of both fetal acidemia and macrosomia.