An elevated pre-pregnancy hemoglobin A1c—which measures average glucose concentration in blood—is related to the more risk of adverse pregnancy outcomes even in women without known diabetes, as reported by a new study published in the current week in PLOS Medicine by Joel Ray of ICES and therefore the University of Toronto, Canada, and colleagues.
Diabetes mellitus and obesity are both related to adverse pregnancy outcomes but the link between pre-pregnancy A1c and severe maternal morbidity or maternal mortality is unknown. In the new study, researchers used data from the province of Ontario spanning 2007 through 2015. The study included data on 31,225 women aged 16 through 50 years with a hospital nascency or stillbirth and who had an A1c measured within 90 days before conception. 28,075 of the ladies (90%) didn’t have a known diagnosis of diabetes.
Overall, the danger of severe maternal morbidity (SMM) or death from 23 weeks gestation to six weeks postpartum was 2.2%. For each 0.5% absolute increase in A1c, the relative risk of SMM or death was 1.16 (95% CI 1.14-1.19, p<0.001) after adjusting for maternal age, multifetal pregnancy, world region of origin, and tobacco/drug dependence. Compared to those with a healthy preconception A1c (below 5.8%), the adjusted relative risk of SMM or death was 1.31 (95% CI 1.06-1.62, p=0.01) in those with a preconception A1c of 5.8-6.4% and 2.84 (95% CI 2.31-3.49, p<0.001) in those with a preconception A1c greater than 6.4%. Among women without a diagnosis of diabetes who had an A1c over 6.4%, the adjusted relative risk was 3.25 (95% CI 1.76-6.00, p<0.001).
The authors note that almost all women don’t undergo A1c testing, which can have led to selection bias among the cohort. Moreover, pre-pregnancy body mass index was unknown for 77% of the participants. Hence, the potential interaction within BMI, A1c and risk of SMM should be examined more. Yet, these findings have implications for pre-pregnancy health screening.
“Given its convenient and widespread use, A1c testing may identify those women with preexisting diabetes mellitus at risk of severe maternal mortality, in a manner similar to its current use in recognizing those at higher risk of fetal anomalies, preterm birth and pre-eclampsia,” the authors say. “As there is no current recommendation about A1c testing in nondiabetic pregnant women, especially those with obesity and/or chronic hypertension, our findings may enhance research about the benefits of A1c screening in these women.”
