Evidence of selection on PGM1 polymorphism in diabetic pregnancy.

Ninety-nine pregnant women with insulin-dependent diabetes mellitus, 83 women with gestational diabetes, and a control sample of 315 nondiabetic consecutive puerperae have been studied along with their newborn infants. Neonatal macrosomia is less frequent among diabetic mothers with phosphoglucomutase (PGM1) genotype PGM1*1/2 than among mothers with other PGM1 genotypes. In gestational diabetes the association is more evident among younger women than among older women. Diabetic women with the PGM11/2 genotype show a reduced proportion of heterozygous PGM11/2 offspring. The phenomenon is much more evident among women under 28 years of age and does not depend on the quality of metabolic control. The data suggest that when both mother and fetus share the PGM11/2 genotype, the deleterious effects of a diabetic environment on fetal development are more severe, leading to an early loss of zygotes. This may contribute to a decrease incidence of macromosomia among live-born infants delivered by PGM11/*2 mothers.