If a woman's blood sugar is elevated during early pregnancy when the foetus’ heart is forming, it raises the risk that the baby will be born with a congenital heart defect, even if the woman doesn’t have diabetes.
According to James Priest, an assistant professor of paediatric oncology and part of a team of researchers from the Stanford University School of Medicine, looking at the glucose values of a pregnant woman during the first trimester could help “measure risk that a child will be born with congenital heart disease” in women who didn’t already have diabetes, including gestational diabetes.
Pregnant women typically receive an oral glucose tolerance test in the second trimester, to establish if they have developed gestational diabetes, but this is long after the foetal heart has developed.
The researchers looked at medical records of almost 20,000 pairs of mothers and their babies born between 2009 and 2015. Records had details on prenatal care including blood test results and cardiac diagnoses 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.
Researchers analysed blood glucose levels from blood samples collected from pregnant mothers between four weeks and 14 weeks of gestation, which were available for 13 per cent of the women.
The researchers also looked at the results of oral glucose tolerance tests performed at 20 weeks of gestation, which were available for just under half of the women in the study.
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 eight per cent for every increase of 10mg per decilitre in blood glucose levels in the early stages of pregnancy, with just over 800 infants captured in the study diagnosed with congenital heart disease.
If these findings are confirmed in a larger sample of women, it might be helpful to measure blood glucose early in pregnancy in all pregnant women to determine who among them is at greater risk of having a baby with a heart defect.
“We could use blood glucose information to select women for whom a screening of the foetal heart could be helpful.
“Knowing about defects prenatally improves outcomes because mothers can receive specialised care that increases their babies’ chances of being healthier after birth,” said Priest. The findings were published in The Journal of Paediatrics.