Glucose Levels Linked to Maternal Mortality Even in Non-Diabetic Women

The prevalence of diabetes mellitus (DM) and obesity have rapidly increased worldwide. Serum glycated hemoglobin A1c (HbA1c), expressed as an absolute percent (e.g., 5.5%), offers a convenient and representative measure of average blood glucose control among individuals with DM.

The relation between pre-pregnancy average glucose concentration and a woman’s risk of severe maternal morbidity (SMM) is unknown. A team of scientists have evaluated whether an elevated preconception hemoglobin A1c (HbA1c) is associated with SMM or maternal death among women with and without known pre-pregnancy diabetes mellitus (DM).

A team of Canadian scientists working with those at the University of Toronto (Toronto, ON, Canada) analyzed data in a study of 31,225 women aged 16 through 50 years with a hospital live birth or stillbirth and who had an HbA1c measured within 90 days before conception. 28,075 of the women (90%) did not have a known diagnosis of diabetes mellitus.

The investigators reported that overall, the risk of severe maternal morbidity (SMM) or death from 23 weeks gestation to 6 weeks postpartum was 2.2%. For each 0.5% absolute increase in HbA1c, the relative risk of SMM or death was 1.16 after adjusting for maternal age, multifetal pregnancy, world region of origin, and tobacco/drug dependence. Compared to those with a healthy preconception HbA1c of below 5.8%, the adjusted relative risk of SMM or death was 1.31 in those with a preconception HbA1c of 5.8-6.4% and 2.84 in those with a preconception HbA1c greater than 6.4%. Among women without a diagnosis of diabetes who had an HbA1c over 6.4%, the adjusted relative risk was 3.25.

The authors concluded that women with an elevated HbA1c, preconception or in early pregnancy, had an increased risk of SMM or death. Given its convenience and widespread use, HbA1c testing may also identify those women with preexisting DM at risk of SMM, in a manner similar to its current use in recognizing those at higher risk of fetal anomalies, preterm birth, and preeclampsia. As there is no current recommendation about HbA1c testing in non-diabetic pregnant women, especially those with obesity and/or chronic hypertension, these findings may enhance the knowledge about the benefits of A1c screening in these women. The study was published on May 19, 2020 in the journal PLOS Medicine.

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