Diabetes is a disorder manifested by high blood sugar levels. It is extremely common in the United States. The prevalence of diabetes is on the rise both in older adults as well as in young people. Unfortunately, poorly controlled diabetes at the time of conception or during early pregnancy is a risk factor for the development of congenital malformations, in particular, congenital heart defects. It is estimated that women with pre-gestational diabetes (diabetes existing prior to pregnancy) have a fivefold increased risk of having a baby with a congenital heart defect compared to the non-diabetic population.

Many studies over the years have confirmed this increased risk. It is thought that high blood sugar in the mother leads to high blood sugar in the developing fetus, creating an abnormal biochemical environment that can negatively affect genes responsible for normal development. The types of congenital heart defects associated with maternal diabetes are those defects that are known to form very early in pregnancy. These include conotruncal abnormalities (truncus arteriosus, tetralogy of Fallot, transposition of the great arteries, double outlet right ventricle), as well as abnormalities that have to do with normal sidedness (heterotaxy syndrome). The incidence of patients born with a ventricular septal defect is also higher in mothers with pre-gestational diabetes.

Studies have confirmed that women who closely monitor and keep their blood sugar in a normal range at the time of conception and early in pregnancy have a much lower risk of having a baby with congenital heart disease compared to women who don’t do this. In addition, preliminary studies in diabetic mice have suggested that antioxidants administered early in pregnancy may also lessen the risk.

Currently the American Heart Association recommends that all pre-gestational diabetic women undergo a fetal echocardiogram between 18 and 22 weeks of age to thoroughly assess the developing baby for the possibility of congenital heart disease.

Penn Laird II, M.D.