Association between changes in glycosylated hemoglobin during the second and third trimesters and adverse pregnancy outcomes among women without hyperglycemia in pregnancy

Objective: To explore the relationship between changes in glycated hemoglobin (HbA1c) during the second and third trimesters and adverse pregnancy outcomes among women without hyperglycemia in pregnancy (HIP). Research design and methods: A total of 1,057 pregnant women who underwent serum HbA1c and delivered at Women's Hospital, Zhejiang University School of Medicine from May 2022 to March 2023, were included in this study. They were divided into four groups. Associations were evaluated using multivariate logistic regression analysis. Results: In our study, an upward trend in HbA1c levels in the second trimester (HbA1c_S) and third trimester (HbA1c_T) among women without HIP was demonstrated. Multivariate logistics regression analysis showed significant associations: Pregnant women with HbA1c_S<5.5 %, HbA1c_T >= 6.1 %, or with HbA1c_S >= 5.5 %, HbA1c_T<6.1 % had a significant correlation with hypertensive disorders of pregnancy (HDP) (aOR:2.72, 95 % CI=1.24-5.97;aOR:2.59, 95 %CI=1.15-5.84). Furthermore, for each 1 % increase in the difference value of HbA1c between the second and third trimesters, the risk of HDP increased about 1.96 times, and the risk of delivering a large-for-gestational-age baby increased about 1.30 times. Conclusion: Among pregnant women without HIP, elevated HbA1c levels in the second or third trimester are associated with increased risks of adverse pregnancy outcomes.