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Updated: Mar 11, 2026

Human Fetal Blood Flow Quantification with Magnetic Resonance Imaging and Motion Compensation
Published on: January 7, 2021
Population-based reference curve for umbilical cord arterial pH in infants born at 28 to 42 weeks
B Skiöld1,2, G Petersson3, M Ahlberg3
1Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
Objective:
The objective of the study was to examine normal variations of umbilical cord arterial pH by gestational age (GA).
Study Design:
Population-based cohort study of 46 199 infants born from 2008 to 2014 in Stockholm, Sweden, with GA 28 to 42 weeks, Apgar score ⩾7 at 5 min, non-instrumental vaginal delivery, and birth weight for GA⩾3rd and ⩽97th percentile. Quantile regression was used to investigate the associations between GA and infant sex, and pH.
Results:
The mean umbilical cord arterial pH (s.d.) was 7.29 (0.10), 7.27 (0.07), 7.25 (0.07) and 7.23 (0.07) among infants born at 28 to 31, 32 to 36, 37 to 41 and 42 weeks, respectively. Arterial pH decreased linearly with increasing GA, and female infants had higher pH than male infants (P<0.001).
Conclusion:
Umbilical cord arterial pH varied in a linear fashion by GA and was influenced by infant sex. The provided reference curve taking GA into account may yield a more accurate definition of acidosis at birth.
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