(437) The impact of weight gain on pregnancy outcomes in patients with low BMI

Thursday, January 30, 2025

4:00 PM – 6:00 PM

Coauthor(s)

TE

Taha Elfarra

Undergraduate student
University of Cincinnati
Cincinnati, Ohio, United States
Leah M. Hefelfinger, MD

Medical Student
University of Cincinnati College of Medicine
Cincinnati, Ohio, United States
JL

Jessica Lin, MD

Cincinnati Children's Hospital Medical Center
Cincinnati, Ohio, United States

Submitting Author and Presenting Author(s)

Braxton Forde, MD

Assistant Professor
University of Cincinnati College of Medicine
Cincinnati, OH, United States

Objective: The association between adverse pregnancy outcomes and obesity is established, however the impact of low maternal weight upon outcomes is much less studied. We sought to evaluate the odds of adverse pregnancy outcomes in the setting of low pre-pregnancy BMI as well as if these risks are mitigated with adequate weight gain in pregnancy.

Study Design: Retrospective cohort study of all United States births in 2021 using National Vital Statistics US birth certificate data. Pregnancy demographics, as well as maternal and neonatal outcomes were compared between a referent group of normal pre-pregnancy BMI with adequate pregnancy weight gain and 3 investigational cohorts: low pre-pregnancy BMI with either adequate, inadequate, or greater than recommended pregnancy weight gain. Multivariate logistical regression models were used to calculate the odds of adverse maternal and neonatal outcomes.

Results: During study period, 520,552 patients had normal pre-pregnancy BMI and adequate weight gain, compared to 40,144 patients 36,650 patients, and 26,155 patients with low pre-pregnancy BMI and adequate, inadequate, or greater than recommended weight gain, respectively. Demographical data was significantly different amongst groups (Table 1). Interestingly, after adjustment for differences in demographics, low pre-pregnancy BMI was associated with adverse neonatal outcomes only when weight gain was inadequate (aOR of composite adverse neonatal outcomes 1.6, 95% CI 1.6-1.7, Figure 1), whereas low pre-pregnancy BMI with either adequate or greater than recommended weight gain has similar neonatal outcomes (aOR 1.0, 1.0-1.0, aOR 1.0, 0.9-1.0, respectively). Of equal interest, low pre-pregnancy BMI was associated with adverse maternal outcomes regardless of weight gain in the pregnancy (Figure 1).

Conclusion: Low pre-pregnancy BMI is associated with adverse neonatal outcomes only in the setting of inadequate pregnancy weight gain, whereas low pre-pregnancy BMI is associated with adverse maternal outcomes regardless of weight gain in the pregnancy.