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HbA1c levels tied to preterm birth in women with type 1 diabetes

The risk for preterm birth among women with type 1 diabetes was strongly associated maternal HbA1c levels around the time of conception, according to a recent study published in the Annals of Internal Medicine.

Researchers also found that mothers who were within the recommended target HbA1C level also appeared to be at risk for preterm birth and other adverse outcomes.

“The possibility exists that glycemia drives a risk for preterm birth even at the currently recommended target HbA1c level,” Jonas F. Ludvigsson, MD, PhD, professor in the department of medical epidemiology at Karolinska Institutet, Stockholm, and colleagues wrote. “However, at less than 6%, we found an increased risk for preterm birth that was similar in magnitude to that found at levels below 6.5%.”

Ludvigsson and colleagues used multiple nationwide Swedish registers to examine HbA1c levels in mothers with type 1 diabetes from January 2003 to December 2014. Preterm birth — defined as less than 37 completed gestational weeks — was the primary outcome. Mothers included in the study were diagnosed with type 1 diabetes prior to conception or up to 91 days following conception and had at least one registered HbA1c measurement 90 days prior to through 91 days after conception.

The cohort included 2,474 births among 2,038 mothers with type 1 diabetes. The reference cohort included 1,165,216 births among 746,916 women without diabetes. Compared with reference mothers, those with type 1 diabetes were more likely to be Nordic, overweight or obese and have a diabetes-related autoimmune disease. Researchers found that 22.3% of births among women with diabetes were preterm, compared with 4.7% of births among women without diabetes.

The adjusted risk ratios for preterm birth among mothers with type 1 diabetes compared with those without diabetes was 2.83 (95% CI, 2.28-3.52) for a periconceptional HbA1c level below 6.5%; 4.22 (95% CI, 3.74-4.75) for levels 6.5% to less than 7.8%; 5.56 (95% CI, 4.84-6.38) for those levels of 7.8% to less than 9.1%; and 6.91 (95% CI, 5.85-8.17) for those with levels 9.1% and over.

“These data are important for developing future guidelines and informing clinicians about the risks associated with poor glycemic control,” Ludvigsson and study authors explained. “However, they do not support the idea that further lowering the recommended HbA1c level during early pregnancy (at least not to 6%) will eliminate the excess risk for preterm birth among women with [type 1 diabetes].” – by Erin Michael

Disclosures: Ludvigsson reports no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures.