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Reference values for umbilical cord arterial pH by mode of birth in preterm, term and postterm infants : a population-based cohort study

Abdulahad, Noor ; Sundberg, Tiia-Marie LU orcid and Zaigham, Mehreen LU orcid (2026) In BMC Pregnancy and Childbirth p.1-11
Abstract
Background
Umbilical cord arterial pH (UApH) is the most objective measurement of the metabolic condition of the infant at birth. However, studies have identified changes in UApH with advancing gestational age, as there is limited data examining UApH changes with different modes of birth. The objective was to establish reference values for UApH according to mode of birth and to investigate the influence of gestational age on changes in UApH across different modes of birth.

Methods
A retrospective cohort study using data from Perinatal Revision South register, from seven maternity units in southern Sweden. Validated pH values from 103,115 infants were included. Cohort characteristics were reported collectively and for each... (More)
Background
Umbilical cord arterial pH (UApH) is the most objective measurement of the metabolic condition of the infant at birth. However, studies have identified changes in UApH with advancing gestational age, as there is limited data examining UApH changes with different modes of birth. The objective was to establish reference values for UApH according to mode of birth and to investigate the influence of gestational age on changes in UApH across different modes of birth.

Methods
A retrospective cohort study using data from Perinatal Revision South register, from seven maternity units in southern Sweden. Validated pH values from 103,115 infants were included. Cohort characteristics were reported collectively and for each mode of birth using numbers and percentages. Reference values were reported as 2.5th to 97.5th percentiles, with mean and median values. One-way ANOVA was used to investigate differences in UApH across different modes of birth. Simple and multiple linear regressions were performed associating gestational age with pH by mode of birth.

Results
Mode of birth in the study population consistent of vaginal non-instrumental (80,957/78.5%), vacuum-assisted (6,486/6.3%), forceps-assisted (429/0.4%), elective Cesarean sections (6,295/6.1%), emergency Cesarean sections (8,180/7.9%), and immediate Cesarean sections (768/0.7%). UApH median values for vaginal non-instrumental births, elective Cesarean sections, and emergency Cesarean sections were 7.240, 7.290, and 7.276 respectively. Lower median values were observed for immediate Cesarean sections (Median = 7.180), vacuum-assisted (Median = 7.170), and forceps-assisted (Median = 7.170) births. A significant negative linear relationship was identified between gestational age and UApH in vaginal non-instrumental, emergency Cesarean sections, and vacuum-assisted vaginal births (P < 0.001).

Conclusion
Reference values were outlined for UApH based on the mode of birth and gestational age. A trend of advancing acidosis was found in infants with increasing gestational age in non-instrumental vaginal births, emergency Cesarean sections, and vacuum-assisted births. Immediate Cesarean sections and instrumental births exhibited higher levels of acidosis. (Less)
Please use this url to cite or link to this publication:
author
; and
organization
publishing date
type
Contribution to journal
publication status
epub
subject
in
BMC Pregnancy and Childbirth
article number
197
pages
1 - 11
publisher
BioMed Central (BMC)
external identifiers
  • pmid:41692718
  • scopus:105030990817
ISSN
1471-2393
DOI
10.1186/s12884-026-08804-z
language
English
LU publication?
yes
id
7e746b9e-c088-45f4-bdab-3f025f1889f0
date added to LUP
2026-02-24 11:53:16
date last changed
2026-04-14 13:15:03
@article{7e746b9e-c088-45f4-bdab-3f025f1889f0,
  abstract     = {{Background<br/>Umbilical cord arterial pH (UApH) is the most objective measurement of the metabolic condition of the infant at birth. However, studies have identified changes in UApH with advancing gestational age, as there is limited data examining UApH changes with different modes of birth. The objective was to establish reference values for UApH according to mode of birth and to investigate the influence of gestational age on changes in UApH across different modes of birth.<br/><br/>Methods<br/>A retrospective cohort study using data from Perinatal Revision South register, from seven maternity units in southern Sweden. Validated pH values from 103,115 infants were included. Cohort characteristics were reported collectively and for each mode of birth using numbers and percentages. Reference values were reported as 2.5th to 97.5th percentiles, with mean and median values. One-way ANOVA was used to investigate differences in UApH across different modes of birth. Simple and multiple linear regressions were performed associating gestational age with pH by mode of birth.<br/><br/>Results<br/>Mode of birth in the study population consistent of vaginal non-instrumental (80,957/78.5%), vacuum-assisted (6,486/6.3%), forceps-assisted (429/0.4%), elective Cesarean sections (6,295/6.1%), emergency Cesarean sections (8,180/7.9%), and immediate Cesarean sections (768/0.7%). UApH median values for vaginal non-instrumental births, elective Cesarean sections, and emergency Cesarean sections were 7.240, 7.290, and 7.276 respectively. Lower median values were observed for immediate Cesarean sections (Median = 7.180), vacuum-assisted (Median = 7.170), and forceps-assisted (Median = 7.170) births. A significant negative linear relationship was identified between gestational age and UApH in vaginal non-instrumental, emergency Cesarean sections, and vacuum-assisted vaginal births (P &lt; 0.001).<br/><br/>Conclusion<br/>Reference values were outlined for UApH based on the mode of birth and gestational age. A trend of advancing acidosis was found in infants with increasing gestational age in non-instrumental vaginal births, emergency Cesarean sections, and vacuum-assisted births. Immediate Cesarean sections and instrumental births exhibited higher levels of acidosis.}},
  author       = {{Abdulahad, Noor and Sundberg, Tiia-Marie and Zaigham, Mehreen}},
  issn         = {{1471-2393}},
  language     = {{eng}},
  month        = {{02}},
  pages        = {{1--11}},
  publisher    = {{BioMed Central (BMC)}},
  series       = {{BMC Pregnancy and Childbirth}},
  title        = {{Reference values for umbilical cord arterial pH by mode of birth in preterm, term and postterm infants : a population-based cohort study}},
  url          = {{http://dx.doi.org/10.1186/s12884-026-08804-z}},
  doi          = {{10.1186/s12884-026-08804-z}},
  year         = {{2026}},
}