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Clinical Obstetrics

Poster Session 4

(1105) Neonatal and Maternal Outcomes in Nulliparas According to Prepregnancy Body Mass Index: A Population-Level Analysis

Wednesday, February 14, 2024
1:00 PM – 2:30 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective:

To compare neonatal and maternal outcomes between BMI (body mass index kg/m2) categories using population-level data and determine the impact lowering or increasing BMI would have on these outcomes.

Study Design:

This was a repeated cross-sectional analysis of US vital statistics Live Birth/Infant Death linked data from 2011 to 2020. We limited analyses to nulliparas with singleton pregnancies who delivered at 20 weeks or greater. Our primary outcome was a composite neonatal outcome defined as any neonatal death, neonatal intensive care unit (ICU), surfactant use, ventilation use, or seizure. Our secondary outcome was severe maternal morbidity defined as any maternal ICU, transfusion, uterine rupture, and hysterectomy. Outcomes were compared according to BMI category (< 18.5, 18.5-24.9, 25-29.9, 30-39.9, 40-49.9, 50-59.9, and 60-69.9) with each of the other categories as the referent. Adjusted relative risks (aRR) with 99% confidence intervals were calculated for each BMI category as a referent group, using modified Poisson regression.

Results:

Of 11,174,890 individuals, 537,541 had BMI < 18.5, 5,569,307 had BMI 18.5-24.9, 2,688,070 had BMI 25-29.9, 1,944,535 had BMI 30-39.9, 382,139 had BMI 40-49.9, 48,432 had BMI 50-59.9 and 4,866 had BMI 60-69.9. Table 1 shows the aRRs for a starting BMI category (referent, column) compared with each of the other categories (row). The following are a few comparisons provided to illustrate the use of the heatmap. Starting with a normal BMI (18.5-24.9), the aRR of the primary outcome increases from 1.02 (yellow) to 2.04 (red) as BMI increases. Starting with a BMI of 60-69.9 the aRR of severe maternal morbidity decreases from 0.51 (or 49% decrease; lime) to 0.34 (or 66% decrease; turquoise) with each decrease in BMI category.

Conclusion:

We provide population-level estimates of the impact of policies to address the obesity epidemic on maternal and neonatal outcomes. Lowering the BMI by even one category would have a tremendous impact on obstetrical outcomes, likely larger than any other proposed intervention.