Purpose: Examine associations between interpregnancy body mass index (BMI) change (difference in the pre-pregnancy BMIs of two consecutive pregnancies) and gestational diabetes mellitus (GDM), pre-eclampsia (PE), gestational hypertension (GHtn), primary cesarean delivery, and vaginal birth after cesarean delivery (VBAC).
Methods: Modified Poisson regression models estimated adjusted associations.
Results: Every 1-unit increase in interpregnancy BMI increased risks of GDM (relative risk [RR]: 1.09; 95% confidence interval [CI], 1.07-1.11), PE (RR: 1.06; 95% CI, 1.04-1.09), GHtn (RR: 1.08; 95% CI, 1.06-1.10), and primary cesarean delivery (RR: 1.03; 95% CI, 1.01-1.05) and decreased the risk of a successful VBAC (RR: 0.98; 95% CI: 0.97-0.997) in the second pregnancy. A BMI increase of ≥3 units increased risks of GDM (RR: 1.71, 95% CI, 1.52-1.93), PE (RR: 1.60, 95% CI, 1.33-1.94), GHtn (RR: 1.66, 95% CI, 1.42-1.94), and primary cesarean delivery (RR: 1.29, 95% CI, 1.12-1.49) and decreased the risk of a successful VBAC (RR: 0.89; 95% CI, 0.80-0.99) compared to women with interpregnancy BMI change within -1 and +1 unit. GDM was also increased among women increasing their BMI by ≥2 but <3 units (RR: 1.40; 95% CI, 1.21-1.61) and among those gaining ≥1 but <2 units (RR: 1.23; 95% CI, 1.08-1.40).
Conclusion: An interpregnancy BMI increase of ≥3 units is associated with an increased risk of all outcomes. These findings emphasize the importance of interpregnancy weight management.
Keywords: Body mass index; Cesarean section; Gestational diabetes; Gestational hypertension; Pre-eclampsia; Vaginal birth after cesarean.
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