Association of maternal body mass index change with risk of large for gestational age among pregnant women with and without gestational diabetes mellitus: a retrospective cohort study.

Objective: To investigate the associations of body mass index (BMI) change and large for gestational age (LGA) among prepregnancy normal-weight women with and without gestational diabetes mellitus (GDM).

Methods: The retrospective study including 9515 normal-weight pregnant women (1331 women with GDM and 8184 without GDM) was conducted in Fujian Maternity and Child Health Hospital in 2020. The BMI change was calculated as gestational weight gain in kilograms by maternal height in meters. The binary logistic regression, stratified analyses, restricted cubic spline models and additive interaction analysis were adopted to reveal the relationship between BMI change and LGA.

Results: Pregnant women with GDM had a lower level of BMI change but a higher incidence of LGA compared with those without GDM. After adjustment for covariates variables, we found that the risk of LGA was associated with the highest quartile of BMI change (OR = 1.89, 95%CI:1.27-2.8 for GDM and OR = 1.48,95%CI:1.27-1.75 for non-GDM). There were significant linear relationships of BMI change and LGA with the inflection point of 5.096 and 5.401 kg/m in GDM and non-GDM groups. Significant additive interaction was observed between parity and BMI change level concerning LGA. A significant difference in BMI change and gestational weight gain (GWG) for LGA prediction was detected.

Conclusion: Higher BMI changes were significantly associated with a higher risk of LGA in pregnant women with or without GDM in a linear dose-response relationship, with the threshold around 5.096 and 5.401 kg/m, respectively. These suggested that BMI changes may be a useful predictor for the incidence of LGA in singleton pregnant women.