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Am J Perinatol
DOI: 10.1055/a-2622-2743
Original Article

Association between Maternal Body Mass Index, Skin Incision-to-Delivery Time, and Umbilical Artery pH in Cesarean Deliveries

Nadine Sunji 
1   Department of Obstetrics and Gynecology, Medical College of Wisconsin, Milwaukee, Wisconsin
,
Alyssa M. Hernandez
1   Department of Obstetrics and Gynecology, Medical College of Wisconsin, Milwaukee, Wisconsin
,
Rachel Schmidt
2   Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin
,
Amy Y. Pan
2   Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin
,
Nina Ayala
3   Department of Obstetrics and Gynecology, Alpert Medical School of Brown University, Providence, Rhode Island
4   Department of Psychiatry and Human Behavior, Alpert Medical School of Brown University, Providence, Rhode Island
,
Margaret H. Bublitz
3   Department of Obstetrics and Gynecology, Alpert Medical School of Brown University, Providence, Rhode Island
4   Department of Psychiatry and Human Behavior, Alpert Medical School of Brown University, Providence, Rhode Island
5   Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island
6   Behavioral and Social Sciences, Brown School of Public Health, Providence, Rhode Island
,
Anna Palatnik 
1   Department of Obstetrics and Gynecology, Medical College of Wisconsin, Milwaukee, Wisconsin
7   Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin
› Author Affiliations
Funding None.
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Abstract

Objective

To estimate the association between maternal body mass index (BMI) at delivery, time from skin incision to infant delivery, and umbilical artery (UA) pH < 7.0.

Study Design

This was a secondary analysis of the Assessment of Perinatal Excellence, a multicenter observational study of an obstetrical cohort of individuals who delivered between 2008 and 2011 in the United States. This analysis included women who delivered via cesarean with known BMI at delivery, skin incision-to-delivery time, and UA pH. Multivariable linear regression assessed the association between BMI and time from skin incision to infant delivery while multivariable logistic regression estimated the associations of BMI and time from skin incision to delivery with UA pH < 7.0. An interaction between BMI and skin incision-to-delivery time was evaluated to examine their combined effect on UA pH < 7.0.

Results

A total of 16,723 women were included across five BMI groups. Increasing BMI was associated with longer time intervals from skin incision to delivery and higher rates of UA pH < 7.0. After controlling for potentially confounding factors, all BMI groups ≥25 kg/m2 were associated with longer time intervals from skin incision to delivery. Specifically, BMI groups of 40 to 49.9 and ≥50 kg/m2 had skin incision-to-delivery times that were 1.30 (95% confidence interval [CI]: 1.23–1.36) and 1.44 (95% CI: 1.34–1.55) times longer, respectively, compared with BMI < 25 kg/m2. In the multivariable logistic regression, BMI group ≥50 kg/m2 remained associated with higher odds of UA pH < 7.0. There was a significant interaction between BMI and time from skin incision to delivery regarding the risk of UA pH < 7.0 (p for the interaction term = 0.003).

Conclusion

Maternal BMI ≥ 50 kg/m2 was associated with a longer time from skin incision to infant delivery and higher odds of UA pH < 7.0. BMI differentially impacted UA pH at different skin incision-to-delivery time intervals.

Key Points

  • Maternal BMI ≥ 25 kg/m2 was associated with longer skin incision-to-delivery times.

  • Maternal BMI ≥ 50 kg/m2 was associated with higher odds of UA pH < 7.0.

  • The effect of maternal BMI on UA pH varied at different skin incision-to-delivery time intervals.

  • Reducing skin incision-to-delivery time may mitigate the risk of UA pH <7.0 in women with BMI ≥50

Keywords

cesarean delivery - neonatal acidosis - obesity - umbilical artery - body mass index - operative time

Note

The findings of this study were presented at the 72nd Annual Meeting of the Society for Reproductive Investigation, Charlotte, NC, March 25-29, 2025.




Publication History

Received: 12 May 2025

Accepted: 26 May 2025

Accepted Manuscript online:
27 May 2025

Article published online:
11 June 2025

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