ABSTRACT 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

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references ACKNOWLEDGEMENTS Professor Sven Cnattingius initiated and conceptualized the research database, and is responsible for the database infrastructure. The work was supported by the

Stockholm County Council (ALF 20130156, 20140105, 20150118 and post-doctoral financial support); and the Swedish Research Council (2013–2429). The funders had no involvement in study design,

collection, analysis, and/or interpretation of data, writing of the report or the decision to submit the paper for publication. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Department of

Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden B Skiöld * Department of Neonatology, Karolinska University Hospital, Stockholm, Sweden B Skiöld *

Department of Medicine Solna, Clinical Epidemiology Unit, Karolinska Institutet, Stockholm, Sweden G Petersson, M Ahlberg, O Stephansson & S Johansson * School of Public Health,

University of California, Berkeley, CA, USA O Stephansson * Department of Clinical Science and Education, Karolinska Institutet, Stockholm, Sweden S Johansson Authors * B Skiöld View author

publications You can also search for this author inPubMed Google Scholar * G Petersson View author publications You can also search for this author inPubMed Google Scholar * M Ahlberg View

author publications You can also search for this author inPubMed Google Scholar * O Stephansson View author publications You can also search for this author inPubMed Google Scholar * S

Johansson View author publications You can also search for this author inPubMed Google Scholar CORRESPONDING AUTHOR Correspondence to S Johansson. ETHICS DECLARATIONS COMPETING INTERESTS The

authors declare no conflict of interest. ADDITIONAL INFORMATION Supplementary Information accompanies the paper on the _Journal of Perinatology_ website SUPPLEMENTARY INFORMATION

SUPPLEMENTARY TABLE 1 (DOCX 35 KB) SUPPLEMENTARY TABLE 2 (DOCX 60 KB) RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Skiöld, B., Petersson, G., Ahlberg,

M. _et al._ Population-based reference curve for umbilical cord arterial pH in infants born at 28 to 42 weeks. _J Perinatol_ 37, 254–259 (2017). https://doi.org/10.1038/jp.2016.207 Download

citation * Received: 28 April 2016 * Revised: 15 September 2016 * Accepted: 12 October 2016 * Published: 01 December 2016 * Issue Date: March 2017 * DOI: https://doi.org/10.1038/jp.2016.207

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