Higher blood sugar early in pregnancy raises the baby’s risk of a congenital heart defect, even among mothers who do not have diabetes, according to a study led by researchers at the Stanford University School of Medicine published in The Journal of Paediatrics.
That babies born to diabetic mothers are prone to heart defects has been known for long. That is why the importance of treating gestational diabetes early is underscored the world over. Gestational diabetes is triggered by the body’s propensity to become resistant to insulin during diabetes so that maximum glucose is available for nourishing the baby. In most mothers the pancreas keeps up and produces extra insulin to compensate but when it cannot, gestational diabetes sets in.
Most women who have a child with congenital heart disease are not diabetic. We found that in women who don’t already have diabetes or develop diabetes during pregnancy, we can still measure risk for having a child with congenital heart disease by looking at their glucose values during the first trimester of pregnancy
The new study is the first to examine this question in the earliest part of pregnancy, when the fetal heart is forming. “Most women who have a child with congenital heart disease are not diabetic. We found that in women who don’t already have diabetes or develop diabetes during pregnancy, we can still measure risk for having a child with congenital heart disease by looking at their glucose values during the first trimester of pregnancy,” said the study’s senior author, James Priest, MD, assistant professor of pediatric cardiology.
One challenge associated with conducting the research was the fact that maternal blood glucose is not routinely measured in nondiabetic pregnant women. Instead, women typically receive an oral glucose tolerance test halfway through pregnancy to determine whether they have gestational diabetes, but this test is performed well after the fetal heart has formed.
The research team studied medical records from 19,107 pairs of mothers and their babies born between 2009 and 2015. The records included details of the mothers’ prenatal care, including blood test results and any cardiac diagnoses made for the babies during pregnancy or after birth. Infants with certain genetic diseases, those born from multiple pregnancies and those whose mothers had extremely low or high body-mass-index measures were not included in the study. Of the infants in the study, 811 were diagnosed with congenital heart disease, and the remaining 18,296 were not.
After excluding women who had diabetes before pregnancy or who developed it during pregnancy, the results showed that the risk of giving birth to a child with a congenital heart defect was elevated by 8 percent for every increase of 10 milligrams per deciliter in blood glucose levels in the early stages of pregnancy.
