Association between mid-to-late pregnancy gestational weight gain and adverse birth outcomes among women with gestational diabetes mellitus

The gestational weight gain (GWG) range during mid-to-late pregnancy associated with the lowest combined risk of adverse birth outcomes in women with gestational diabetes mellitus (GDM) remains unclear. This study aims to examine the associations between GWG and adverse birth out-comes among women with GDM.

This study included a cohort of 1,673 pregnant women with GDM. GWG was defined as weight gain from pre-pregnancy to a measurement between 24 and 32 gestational weeks, residualized for gestational age and standardized as z-scores. Multivariable logistic regression models were used to assess associations between GWG z-scores (per 1-SD increase and categories: <-1, -1 to 1 [reference], and ≥1) and small for gestational age (SGA), large for gestational age (LGA), and preterm birth. Restricted cubic splines were fitted to explore nonlinear associations.

Each 1-SD higher in GWG z-score was associated with lower odds of SGA (odds ratio [OR], 0.55; 95% confidence interval [CI], 0.43-0.71) and higher odds of LGA (1.48; 1.29-1.70). Compared with the reference group, women with GWG z-scores <-1 had higher odds of SGA and lower odds of LGA, whereas those with z-scores ≥1 showed the opposite pattern. No significant association was observed with preterm birth. Spline analyses indicated that a GWG z-score of approximately -0.07 (equal to 8.2 kg at 28 weeks) was associated with the lowest combined odds of SGA and LGA.

Among women with GDM, both insufficient and excessive mid-to-late pregnancy GWG were associated with adverse size-for-gestational-age outcomes.