Strength of association between umbilical cord pH and perinatal and long term outcomes: systematic review and meta-analysisBMJ 2010; 340 doi: https://doi.org/10.1136/bmj.c1471 (Published 13 May 2010) Cite this as: BMJ 2010;340:c1471
- Gemma L Malin, clinical research fellow1,
- Rachel K Morris, clinical research fellow1,
- Khalid S Khan, professor of obstetrics, gynaecology, and clinical epidemiology12
- 1Department of Obstetrics, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham
- 2Department of Obstetrics and Gynaecology, Birmingham Women’s Foundation NHS Trust, Birmingham
- Correspondence to: G L Malin, Academic Department of Obstetrics and Gynaecology, Birmingham Women’s Hospital, Edgbaston, Birmingham B15 2TG
- Accepted 14 February 2010
Objective To evaluate the association between umbilical cord pH at birth and long term outcomes.
Design Systematic review and meta-analysis.
Data sources Medline (1966-August 2008), Embase (1980-August 2008), the Cochrane Library (2008 issue 8), and Medion, without language restrictions; reference lists of selected articles; and contact with authors.
Study selection Studies in which cord pH at birth was compared with any neonatal or long term outcome. Cohort and case-control designs were included.
Results 51 articles totalling 481 753 infants met the selection criteria. Studies varied in design, quality, outcome definition, and results. Meta-analysis carried out within predefined groups showed that low arterial cord pH was significantly associated with neonatal mortality (odds ratio 16.9, 95% confidence interval 9.7 to 29.5, I2=0%), hypoxic ischaemic encephalopathy (13.8, 6.6 to 28.9, I2=0%), intraventricular haemorrhage or periventricular leucomalacia (2.9, 2.1 to 4.1, I2=0%), and cerebral palsy (2.3, 1.3 to 4.2, I2=0%).
Conclusions Low arterial cord pH showed strong, consistent, and temporal associations with clinically important neonatal outcomes that are biologically plausible. These data can be used to inform clinical management and justify the use of arterial cord pH as an important outcome measure alongside neonatal morbidity and mortality in obstetric trials.
Zainab Laftah helped with data extraction. Richard Riley provided statistical expertise and advice.
Contributors: GLM designed the review; extracted, analysed, and interpreted the data, drafted the article; and is responsible for the integrity of the work. She is the guarantor. RKM extracted and interpreted the data, revised the article critically for intellectual content, and approved the final draft for publication. KSK conceived the review, helped analyse and interpret the data, revised the article critically for intellectual content, and approved the final draft for publication.
Funding: GLM is funded by the Mary Crosse fellowship, Birmingham Women’s Foundation Trust. RKM is funded by a Medical Research Council/Royal College of Obstetrics and Gynaecology clinical research training fellowship (RRAK12923).
Competing interests: All authors have completed the unified competing interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare (1) no financial support for the submitted work from anyone other than their employer; (2) no financial relationships with commercial entities that might have an interest in the submitted work; (3) no spouses, partners, or children with relationships with commercial entities that might have an interest in the submitted work; and (4) no non-financial interests that may be relevant to the submitted work.
Ethical approval: Not required.
Data sharing: The odds ratios for outcomes included in table 1 but not reported in the paper are available from the author on request.
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