Association of higher HbA1c within the normal range with adverse pregnancy outcomes: a cross-sectional study

The aim of this study was to investigate the association between a relatively high HbA1c level within the normal range and the risk of adverse pregnancy outcomes. This retrospective cohort study was conducted between March 2018 and March 2019 at Women’s Hospital, School of Medicine, Zhejiang University. Multiple logistic regression models after adjusting for plausible confounders were implemented to assess the relationships between the level of HbA1c and adverse pregnancy outcomes. A total of 8585 women were included in our study. The rates of preterm birth, macrosomia and preeclampsia were 4.4% (380/8585), 5.3% (457/8585) and 1.7% (149/8585), respectively. After adjusting for potential confounding variables, an HbA1c range of 5.5–5.9% (37–41 mmol/mol) remained significantly associated with an increased risk of preterm delivery (a-OR 2.27; 95% CI, 1.50–3.43), macrosomia (a-OR 1.97; 95% CI, 1.32–2.94) and preeclampsia (a-OR 3.70; 95% CI, 2.07–6.60). GDM-negative pregnant women with an HbA1c level in the range of 5.5–5.9% (37–41 mmol/mol) had an increased risk of preterm delivery (a-OR 2.84; 95% CI, 1.71–4.71) and preeclampsia (a-OR 3.82; 95% CI, 1.81–8.04). However, GDM-positive pregnant women had an increased risk of macrosomia (a-OR 2.12; 95% CI, 1.13–3.97) and preeclampsia (a-OR 2.62; 95% CI, 1.01–6.81). A higher HbA1c level within the normal range is an independent risk factor for preterm delivery and preeclampsia, especially among GDM-negative women. Therefore, relevant medical staff should enhance the awareness of risk and prevention to strengthen pregnancy monitoring.