The review concluded that delayed cord clamping resulted in limited benefits in term deliveries when compared with early cord clamping. For preterm deliveries, delayed cord clamping significantly reduced risk of intraventricular haemorrhage and provided marginal hemodynamic benefits for neonates. Given the potential for bias, heterogeneity and a limited quality evidence base, the authors' conclusions should be treated with caution.

To assess the effects of delayed cord clamping compared to early cord clamping at delivery on maternal and infant short-term and long-term outcomes.

MEDLINE and The Cochrane Library were searched up to December 2010 for relevant studies; limited search terms were reported. The reference lists of retrieved studies and recent conference proceedings were also searched.

Randomised controlled trials (RCTs) that compared delayed cord clamping (defined as over 30 seconds after delivery) with early cord clamping (within 30 seconds of delivery) which reported maternal and/or infant outcomes were eligible for the review. Abstracts without data were excluded.

Included studies were divided into those where delivery was at term (most participants were listed as over 37 weeks) or pre-term (under 37 weeks). The definition of early cord clamping was fairly uniform across trials (ranging from immediate action to below 30 seconds) but delayed cord clamping was defined in multiple ways. Studies were undertaken worldwide (four in the United Kingdom). Most trials that assessed term delivery were undertaken in developing countries, but all were conducted in settings with facilities for managing potential adverse events.

The authors did not state how many reviewers selected studies for the review.

Studies were assessed for quality using the Cochrane risk of bias tool; criteria included randomisation, allocation concealment, blinding, completeness of outcome reporting and absence of selective outcome reporting. Overall scores were calculated, but not reported.

The authors did not state how many reviewers assessed studies for quality.

Data were extracted to enable the calculation of relative risks (RRs) and mean differences (MDs), with 95% confidence intervals (CIs).

The authors did not state how many reviewers extracted data.

Effect sizes were pooled in meta-analyses (methods not reported) and 95% confidence intervals were calculated. Sensitivity analysis was planned to assess the effects of study quality on results.

Twenty-nine RCTs (4,504 participants) were included in the review. Fifteen RCTs assessed the effects on term deliveries and 14 on preterm deliveries. Adequate allocation concealment was reported in 20 studies; the remainder of risk of bias outcomes were scored adequate in approximately half of the studies. Four of 15 term RCTs and seven of 14 preterm RCTs had low risk of bias; the remainder had either moderate or high risk of bias.

Term deliveries: Compared to early cord clamping, delayed cord clamping was associated with significantly increased initial haematocrit at birth (MD 2.38, 95% CI 1.10 to 3.67; six trials), initial haemoglobin at birth (MD 1.95, 95% CI 0.81 to 3.10; four trials), ferritin level (MD 17.00, 95% CI 12.15 to 21.85; four trials) and reduced need for manual removal of placenta (RR 0.45, 95% CI 0.22 to 0.94; two trials). There was no evidence of significant differences between groups for other outcomes.

Pre-term deliveries: Compared to early cord clamping, delayed cord clamping was associated with significantly increased haematocrit at birth (MD 3.04, 95% CI 2.58 to 3.51; nine trials), peak serum bilirubin (mg/dL) (MD 0.91, 95% CI 0.21 to 1.60; five trials), increased mean blood pressure (MD 3.66, 95% CI 0.74 to 6.58; two trials), increased haemoglobin at longest follow up (MD 1.10, 95% CI 0.35 to 1.85; one trial), increased haematocrit at follow up (MD 4.00, 95% CI 0.53 to 7.47; one trial) and reduced number of transfusions (MD -0.92, 95% CI -1.78 to - 0.05; four trials). With delayed cord clamping there was also a significantly reduced requirement for transfusions (RR 0.72, 95% CI 0.54 to 0.96; six trials) and reduced risk of intraventricular haemorrhage (RR 0.49, 95% CI 0.32 to 0.74; seven trials).

There were too few studies to undertake sensitivity analysis in term delivery studies. In preterm studies, risk of mortality and haemorrhage were not markedly changed when only studies at low risk of bias were assessed.

Compared to early cord clamping, delayed cord clamping in term deliveries resulted in very limited benefits for infants and did not significantly increase complications or provide benefits for mothers. For preterm deliveries, delayed cord clamping results in significantly reduced risks of intraventricular haemorrhage and provided marginal haemodynamic benefits for neonates, with unknown effects on mothers.

The review addressed a clearly specified research question, supported by broad inclusion criteria with multiple outcomes. Relevant sources were searched for published and unpublished studies, which minimised the chance of publication bias. The authors did not state how many reviewers selected studies, extracted data or assessed studies for quality, so reviewer error and bias could not be excluded. A valid tool was used to assess studies for quality; most had low to moderate overall quality scores. In the statistical synthesis of studies, no assessment of heterogeneity was reported, which made it difficult to evaluate the robustness of the findings. Publication bias was not formally assessed, which made it unclear if studies were missed.

The authors acknowledged that delayed cord clamping was defined in multiple ways, which lead to potential heterogeneity with caution required in the interpretation of results. They also acknowledged that other variables, not reported in the review (position of the infant following delivery, administration of an uterotonic drug during the third stage, and type of delivery), could have an impact on findings. Given the potential for bias and heterogeneity in the review and an evidence base of generally limited quality, the authors' conclusions should be treated with caution.

Practice: The authors did not state any implications for practice.

Research: The authors did not state any implications for research.

No funding.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.