(1175) Association between maternal pre-pregnancy BMI category and fetal umbilical artery pH

Friday, February 10, 2023

3:30 PM – 5:00 PM

Objective: To evaluate the association between maternal pre-pregnancy body mass index (BMI kg/m²) and fetal umbilical arterial pH at the time of delivery in nulliparous women.

Study Design: We performed a secondary analysis of the nuMoM2b study. Subjects in this study were nulliparous with a singleton pregnancy. Subjects with fetal anomalies or missing fetal umbilical artery pH were excluded. Subjects were categorized based on pre-pregnancy BMI (less than 18.5, 18.5-24.9, 25-29.9, 30-34.9, 35-39.9, and 40 or greater). Our primary outcome was an umbilical artery pH at the time of delivery. We also examined base deficit, the rate of fetal acidosis defined as pH < 7.0, and the need for advanced neonatal resuscitation. Analyses were stratified by the route of delivery. Multivariable linear or logistic regression models were used to calculate adjusted P-values or adjusted odds ratios (95% confidence intervals), controlling for confounders.

Results: Of 3,015 subjects, 1,870 (62%) had a vaginal delivery, and 1,145 (38%) had a cesarean delivery. There were significant differences in demographics across the BMI categories in both subjects who had a vaginal delivery and cesarean delivery (age, race, chronic hypertension, gestational diabetes, pregestational diabetes, preeclampsia, and gestational hypertension). Among subjects who had a vaginal delivery, there was no difference in fetal umbilical artery pH (p=0.31) across the BMI categories (Table 1). Base deficit of subjects with BMI < 18.5 and BMI 40 or greater was significantly lower than that of subjects with BMI 18.5-24.9 (adjusted p< 0.05). Among subjects who had a cesarean delivery, the fetal umbilical arterial pH of subjects with BMI 30-34.9 and BMI 40 or greater was significantly lower than that of subjects with BMI 18.5-24.9 (adjusted p< 0.05) (Table 2).

Conclusion: In nulliparous subjects with a singleton pregnancy, obesity was associated with decreased fetal umbilical arterial pH at the time of cesarean delivery. However, this finding was not observed in subjects who had a vaginal delivery.

Primary & Presenting Author(s)

TD
Tracey DeYoung, MD
Maternal-Fetal Medicine Fellow
Eastern Virginia Medical School
Norfolk, Virginia, United States

Coauthor(s)

LN
Lea Nehme, MD
Eastern Virginia Medical School
Norfolk, VA, United States
Alfred Abuhamad, MD
President, Provost and Dean
Eastern Virginia Medical School
Norfolk, Virginia, United States
Tetsuya Kawakita, MD, MS, FACOG
Assistant professor
Eastern Virginia Medical School
Norfolk, Virginia, United States