(703) Comparison of Change in BMI vs Gestational Weight Gain on Maternal and Neonatal Outcomes

Institute of Medicine (IOM) guidelines for gestational weight gain (GWG) do not account for maternal height as a specific measure. We sought to determine if change in BMI (ΔBMI) during pregnancy correlates more with birthweight (BW) and unplanned cesarean delivery (uCD) than GWG outside of the IOM guidelines.

 

Study Design: All women delivering at a major inner-city hospital from May to December 2021 were included. Women with unknown GWG, preterm birth, multiple gestation or anomalies were excluded. ΔBMI categories were defined as decrease (< -0.5), no change (-0.5 to +0.5), min (0.6-5.0), mod (5.1-10), and excess ( >10). Fisher’s exact test and ANOVA were used to report significance when appropriate and logistical regression modeling was used to test the effects of ΔBMI and GWG on BW and uCD; a significance level of 0.05 was used. Min ΔBMI and GWG within IOM guidelines were used as reference.

Results:

1,555 women met inclusion criteria.  No significant differences were seen for race, ethnicity or insurance type among groups. As expected, higher pre-pregnancy BMI (pre-BMI) was associated with greater BW. GWG above IOM was protective against BW < 2500g compared to within IOM guidelines (OR 0.51, CI 0.26-0.98).  In normal, overweight and obese women, larger ΔBMI was associated with increasing BW but not BW > 4000g. GWG above IOM guidelines was associated with increased odds of uCD (OR 1.42, CI 1.04-1.93) after adjusting for pre-BMI, but GWG outside IOM was not associated with uCD after adjusting for pre-BMI and ΔBMI.  Odds of uCD was significantly increased with mod ΔBMI (OR 1.83, CI 1.38-2.43) and excess ΔBMI (OR 2.05, CI 1.01-4.17), while risk of uCD decreased with no change in ΔBMI (OR 0.28, CI 0.09-0.93) compared to min ΔBMI after adjusting for pre-BMI; ORs were similar for ΔBMI in the model adjusting for GWG outside IOM and pre-BMI.

 

Conclusion:

While ΔBMI is not predictive of macrosomia, ΔBMI had a stronger association with unplanned CD than GWG outside IOM guidelines. Future prospective studies are needed to confirm the utility of ΔBMI and maternal height in risk assessment for unplanned CD.