Preconception Glycemic Control: Reducing Risk of Congenital Heart Defect in Offspring

Congenital heart defects (CHD) are among the most common birth defects and a leading cause of infant mortality. Pregestational diabetes mellitus increases risk of fetal CHD. However, this association and prevention implications have not been integrated across literature. This narrative review seeks to combine evidence of cardiac formation and biological mechanisms that frame maternal hyperglycemia as a teratogen of cardiogenesis, as well as preconception care (PCC) recommendations for diabetic women. Cardiac neural crest cells are vulnerable to glycemia-induced oxidative stress, apoptosis, and epigenetic abnormalities before cardiac septation is complete by the seventh week of gestation. CHD risk rises at maternal HbA1c levels starting from 5.6%, below the minimum for prediabetes. As the window for hyperglycemia’s teratogenic effect may close before pregnancy is confirmed, glycemic control during pregnancy is unlikely to reduce much risk of CHD, while PCC can have greater influence in reducing first-trimester HbA1c levels, lowering risk of congenital defects. Little evidence exists isolating risk of CHD from risk of fetal malformations. Disparities in access to clinical care limit the improvement it could bring to odds of CHD-free birth. Bridging gaps in evidence and implementation is crucial for bringing evidence into PCC for CHD prevention based on glycemic control.