Diabetes quadruples risk of birth defects, study shows
Diabetic mothers-to-be have a high risk of giving birth to babies with birth defects like congenital heart disease and spina bifida — specifically, a risk four-fold higher than non-diabetic mothers.
That’s according to new findings from a British study that analyzed data from more than 400,000 pregnancies in northeast United Kingdom that occurred from 1996 to 2008.
For the study, researchers from the Newcastle University compared the rates of birth defects in babies born to women with diabetes (numbering 1,677) to those that women without diabetes had. Most of the diabetic women studies (78.4 percent ) had type 1 diabetes.
Researchers found that about seven percent of babies born to diabetic women were affected by birth defects that were not genetic, or caused by problems with the number or structure of the chromosomes or cell structures containing our DNA. This was 3.8 times higher than the rate in women without diabetes.
“Many of these anomalies happen in the first four to six weeks,” Dr. Ruth Bell from Newcastle University, lead researcher, told the BBC.
The study also found that having worse control over their blood sugar around the time of conception increased the risk that babies will be born with defects.
Conversely, by controlling blood sugar, researchers found, a diabetic woman could significantly lower the chance that her child will have a birth defect.
“The risk of problems can be reduced by taking extra care to have the best possible glucose control before becoming pregnant,” Dr. Bell said.
“The good news is that, with expert help before and during pregnancy, most women with diabetes will have a healthy baby,” she added.
But in a comment on the study, U.K.’s National Health Service said that, as soon as they are teenagers, diabetic women should be informed that they can reduce the risks of birth defects — but these can’t eliminated entirely.
Quantifying the birth defect risk
Type 1 diabetes is inherited and tends to appear in childhood, while type 2 diabetes is often brought about by a poor diet and lack of exercise. Both types lead to uncontrolled levels of sugar in the bloodstream.
Health experts have long known that problems with blood sugar causes problems in pregnancy ranging from the baby being overweight due to too much sugar, to miscarriage, stillbirth, neonatal death and birth defects.
This new study, conducted by the Newcastle researchers in coordination with the Regional Maternity Survey Office in Newcastle, and the South Tees NHS Trust, provides new evidence.
Specifically, the cohort study, published in the journal Diabetologica, quantifies the link between diabetes and birth defects.
It clarified the extent to which diabetes increased the risk of major birth defects, and how this risk is affected by other factors such as maternal age, smoking and socioeconomic status.
Blood sugar control is often calculated using a measure called HbA1c, which represents the levels of hemoglobin in the blood with a sugar molecule attached.
Doctors generally try to keep HbA1c levels below seven percent, and for women who want to have babies, they advise keeping the levels below 6.1 percent even before trying to have a baby.
The new study shows that each increase of one percent in HbA1c over 6.3 percent is associated with a 30 percent increase in the odds of birth defects:
• HbA1c level was 6.1% = a woman had a one in 34 chance that she’d have a birth defect
• 7% = One in 26
• 8% = One in 17
• 9% = One in 12
• 10% = One in nine
Women who already had kidney problems as a result of their diabetes also had a further increased risk of having babies with birth defects—but researchers said this needs to be studied further.
The researchers found that other factors associated with an increased risk of birth abnormalities—such as low intake of folic acid and lower socioeconomic status—were not statistically significant.
Commenting on the study, U.K.’s National Health Service said the study’s strengths were in its being a large-size study that enrolled the entire population in the study area. This raises the chance that the study findings more accurately reflect real-life conditions.