Edinburgh Napier University

  Background
Practices related to umbilical cord clamping at birth should be evidence-based. Deferred cord clamping, compared to immediate cord clamping, shows benefits for preterm neonates but this may also apply to healthy term neonates. Different blood sampling techniques are used to measure effect of deferred and immediate cord clamping.

Objective
To assess the statistical and effect size differences between blood biomarkers from umbilical cord and capillary blood samples of healthy term neonates following either immediate or deferred cord clamping.

Design
Systematic review and meta-analysis.

Methods
The databases PubMed, Medline, CENTRAL, CINAHL and EMBASE were systematically searched. We included studies with a randomised clinical trial design comparing deferred and immediate cord clamping among healthy term neonates born by a spontaneous vaginal birth, reporting on blood biomarkers. Studies including caesarean births and premature births/neonates were excluded. Study attributes, sampling technique, blood biomarkers, mean differences, and standard deviations were extracted. The standardised mean differences (SMD) and sampling errors were calculated for effect size estimation. Meta-analyses were performed if ≥ 2 studies reported the same outcome using RevMan 5. Subgroup analyses distinguished effects from umbilical cord and capillary blood samples. Moderator tests and publication bias analyses were performed using JASP.

Results
Thirteen studies were included for analysis. The biomarkers haematocrit, haemoglobin, and bilirubin were reported in ≥ 2 studies and thus eligible for pooling. No differences were found in haemoglobin (SMD 0.05, 95%CI -0.73 to 0.82) or bilirubin values (SMD 0.03, 95%CI -0.24 to 0.31) between umbilical cord blood samples collected after deferred or immediate cord clamping. Deferred cord clamping led to lower haematocrit values (SMD -0.3, 95%CI -0.53 to − 0.07). Higher haematocrit (SMD 0.67, 95%CI 0.37 to 0.97) and haemoglobin values (SMD 0.75, 95%CI 0.42 to 1.09) from capillary blood samples, collected 2 to 72 h postpartum, showed when cord clamping was deferred. No effect was found on bilirubin values (SMD 0.13, 95%CI -0.09 to 0.36) irrespective of the sampling technique.

Conclusions
Blood collected after deferred umbilical cord clamping showed increased haemoglobin and haematocrit values up to 72 h after birth, opposed to bilirubin values. Clinical evaluation of blood biomarkers from the umbilical cord shows different values compared to capillary blood. Sampling time and technique therefore seem essential in estimating the effects of deferred cord clamping.