Risk of preterm birth in mothers with type 1 diabetes strongly linked to HbA1c levels

DELHI: In women with type 1 diabetes (T1D), the risk for preterm birth is strongly associated with periconceptional HbA_1c levels, finds a recent study.

The study, published in the journal Annals of Internal Medicine further found that women with HbA_1c levels within the recommended target levels were also at increased preterm birth risk.

Presence of T1D diabetes in mother is linked to preterm birth and other adverse pregnancy outcomes. However, there are no studies on how these risks vary with HbA_1c levels. Jonas F. Ludvigsson, a professor in the department of medical epidemiology at Karolinska Institutet, Stockholm, and colleagues examined preterm birth risk according to periconceptional HbA_1c levels in women with T1D from January 2003 to December 2014 by using multiple nationwide Swedish registers.

Preterm birth — defined as less than 37 completed gestational weeks — was the primary outcome. Mothers included in the study were diagnosed with T1D prior to conception or up to 91 days following conception and had at least one registered HbA1c 90 days prior to through 91 days after conception.

Also Read: Early screening for gestational diabetes not beneficial, Study refutes ACOG guidance

Key findings of the study include:

• Preterm birth occurred in 552 (22.3%) of 2474 infants born to mothers with T1D versus 54 287 (4.7%) in 1 165 216 infants born to mothers without diabetes.


• The incidence of preterm birth was 13.2% in women with a periconceptional HbA_1c level below 6.5% (adjusted risk ratio [aRR] vs. women without T1D, 2.83 , 20.6% in those with a level from 6.5% to less than 7.8% (aRR, 4.22, 28.3% in those with a level from 7.8% to less than 9.1% (aRR, 5.56 [CI, 4.84 to 6.38]), and 37.5% in those with a level of 9.1% or higher (aRR, 6.91).


• The corresponding aRRs for medically indicated preterm birth (n = 320) were 5.26, 7.42, 11.75, and 17.51, respectively.


• The corresponding aRRs for spontaneous preterm birth (n = 223) were 1.81, 2.86, 2.88, and 2.80, respectively.


• Increasing HbA_1c levels were associated with the study's secondary outcomes: large for gestational age, hypoglycemia, respiratory distress, low Apgar score, neonatal death, and stillbirth.

Also Read: Undiagnosed diabetes during pregnancy increases risk of stillbirths

"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.

For detailed study log on to DOI: 10.7326/M18-1974