Maternal overweight and obesity increase the risk of fetal acidosis during labor
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Updated: Feb 8, 2026

Isolation of Leukocytes from the Murine Tissues at the Maternal-Fetal Interface
Published on: May 21, 2015
Stefan Johansson1,2, Anna Sandström3, Sven Cnattingius3
1Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden. stefan.johansson@ki.se.
Objective:
To investigate whether maternal overweight and obesity increased the risk of fetal acidosis measured in umbilical cord arterial blood after delivery.
Study Design:
Population-based cohort study of 84,785 term (≥37 weeks) infants. Logistic regression was used to estimate risks of fetal acidosis in umbilical cord arterial blood. Fetal acidosis was defined as pH <7.10 or as pH <1st percentile on a normal reference curve.
Result:
Risks of fetal acidosis increased, regardless of definition, with maternal overweight and obesity severity. Compared to normal weight (BMI 18.5-<25), the odds ratios (95% confidence interval) for pH <7.10 were 1.35 (1.23-1.47) for overweight (BMI 25-<30), 1.46 (1.27-1.69) for mild obesity (BMI 30-<35), and 1.75 (1.42-2.15) for severe obesity (BMI ≥35). The association for obesity was attenuated in analyses restricted to non-instrumental vaginal deliveries.
Conclusion:
Maternal overweight and obesity increased the risk of fetal acidosis. More complicated deliveries in obese women may partially explain this association.
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