ABSTRACT
Gestational diabetes mellitus (GDM) aggregates in families. The cause of this clustering with first-degree relatives who have previously had either GDM or another form of diabetes is likely to have genetic, epigenetic, and environmental components, especially given that in females both low and high birth weights are associated with the future development of GDM.1 Therefore, a woman who is pregnant and has poorly controlled, preexisting type 1 diabetes has an increased risk of delivering a macrosomic offspring due to her increased blood glucose concentrations crossing the placenta and stimulating the release of insulin, which then acts as a foetal growth factor. The high birth weight offspring, if female, is herself at increased risk of subsequently developing GDM or type 2 diabetes2 in the reproductive years and beyond. In addition to such metabolic programming effects, common genetic variation also regulates size at birth,3 and therefore future GDM risk in babies born with high or low birth weights.
