Despite treatment, HbA1c > 37mmol/mol in the first trimester is associated with premature delivery among South Asian women with gestational diabetes mellitus: a retrospective cohort study

Abstract

Purpose: To examine the effects of first-trimester HbA1c (HbA1c-FT) >37mmol/mol on preterm birth (PTB) and large-for-gestational-age (LGA) babies in a retrospective cohort of South Asian pregnant women with gestational diabetes (GDM). Methods: The cohort (n = 686) was separated into two groups based on HbA1c-FT values: Group A (n=97) and Group B (n=589), with values of 37-46 mmol/mol (5.5-6.4%) and <37 mmol/mol (5.5%), respectively. HbA1c-FT's independent influence on PTB and LGA babies was examined using multivariable logistic regression in groups A and B women. The reference group (Group C) included 2031 non-GDM women with HbA1c-FT <37 mmol/mol (<5.5%). The effects of HbA1c-FT on PTB and LGA babies in obese women in Groups A, B, and C (designated as A-ob, B-ob, and C-ob, respectively) were re-analyzed using multivariable logistic regression. Results: Group A GDM women with greater HbA1c-FT had a higher risk for PTB (aOR: 1.90, 95% CI: 1.12 to 3.20) but not LGA babies (aOR: 1.20, 95%: 0.74 to 1.95). The risk of PTB was higher for obese women in Group A-ob: aOR 3.15 [95% CI 1.62 to 6.15]. However, GDM women with normal HbA1c-FT exhibited no elevated risk for PTB: Groups B and B-ob had aORs of 1.17.(95% CI 0.89 to 1.55) and 1.29 (95% CI 0.84 to 1.97) respectively. Conclusions: South Asian GDM women with prediabetic HbA1c FT; 37-46 mmol/mol (5.5-6.4%) are more likely to deliver preterm babies despite treatment, while the risk for LGA babies was the same as non-GDM women.