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07-09-2018 | Pregnancy | News

Periconception glycemic control impacts cardiac birth defect risk

medwireNews: The infants of mothers with type 1 diabetes have at least twice the risk for cardiac birth defects as those of mothers without diabetes, with the risk increasing with poorer glycemic control around the time of conception, Swedish study data show.

The risk for noncardiac birth defects, however, was not significantly increased, report Jonas Ludvigsson (Karolinska Institutet, Stockholm) and co-authors in The BMJ.

The findings arose from an analysis of 2458 singleton infants of mothers with type 1 diabetes who had a glycated haemoglobin (HbA1c) measurement within 3 months before or after the estimated time of conception, and 1,159,865 infants of mothers without diabetes.

During the 12-year study period, there were 122 cases of major cardiac defects observed among the infants of mothers with type 1 diabetes.

There were 15 cases of major cardiac defects per 1000 infants of mothers without diabetes, compared with 33 per 1000 for infants of mothers with type 1 diabetes and a HbA1c level below 6.5%, 49 per 1000 for a HbA1c level of 6.5% to less than 7.8%, 44 per 1000 for a level of 7.8% to less than 9.1%, and 101 per 1000 for mothers with a HbA1c of 9.1% or higher around the time of conception.

This corresponded to significant 2.17-, 3.17-, 2.79-, and 6.23-fold increased risks for major cardiac birth defects with each increasing HbA1c category, after adjustment for potential confounders such as calendar year of conception, maternal age, parity, BMI, smoking status, and other autoimmune diseases.

By contrast, the risk for major noncardiac defects was not statistically significantly increased at any of the four HbA1c levels examined.

Overall, there were 50 cases of major noncardiac defects observed among infants of mothers with type 1 diabetes.

Compared with 18 cases of major noncardiac defects per 1000 infants of mothers without diabetes, the rates among infants of mothers with type 1 diabetes were 22 per 1000 for a HbA1c level below 6.5%, 19 per 1000 for a level of 6.5% to less than 7.8%, 17 per 1000 for a level of 7.8% to less than 9.1%, and 32 per 1000 for a level of at least 9.1%.

However, the researchers point out that the small number of major noncardiac defects meant the study had limited statistical power to detect differences for this outcome, and note that they only looked at live births.

Ludvigsson et al conclude that their study “confirms previous findings, providing robust evidence for an association between worse periconception glycaemic control in type 1 diabetes and a progressive increase in the risk of birth defects.”

They add that it demonstrates that the association is “driven by cardiac defects and also that women with type 1 diabetes who have a periconception glycated haemoglobin level within target levels recommended by guidelines were at a substantially increased risk of delivering infants with major cardiac defects.”

By Laura Cowen

medwireNews is an independent medical news service provided by Springer Healthcare. © 2018 Springer Healthcare part of the Springer Nature group

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