Strength of association between umbilical cord pH and perinatal and long term outcomes: systematic review and meta-analysis

Gemma L Malin, Rachel K Morris, Khalid S Khan, Gemma L Malin, Rachel K Morris, Khalid S Khan

Abstract

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, I(2)=0%), hypoxic ischaemic encephalopathy (13.8, 6.6 to 28.9, I(2)=0%), intraventricular haemorrhage or periventricular leucomalacia (2.9, 2.1 to 4.1, I(2)=0%), and cerebral palsy (2.3, 1.3 to 4.2, I(2)=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.

Conflict of interest statement

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.

Figures

https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4787867/bin/malg700435.f1_default.jpg
Fig 1 Study selection process
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4787867/bin/malg700435.f2_default.jpg
Fig 2 Association of low arterial cord pH with neonatal mortality. EPI=estimated predictive interval
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4787867/bin/malg700435.f3_default.jpg
Fig 3 Association of low arterial cord pH with neonatal morbidity. HIE=hypoxic ischaemic encephalopathy; IVH=intraventricular haemorrhage; PVL=periventricular leucomalacia; NS=not stated; WM=cerebral white matter; EPI=estimated predictive interval
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4787867/bin/malg700435.f4_default.jpg
Fig 4 Association of low arterial cord pH with cerebral palsy. NS=not stated; EPI=estimated predictive interval

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