A Cochrane review included 15 studies with a total of 738 infants. The maximum delay in cord clamping was 180 seconds. Delayed cord clamping was associated with fewer transfusions for anaemia RR 0.61, 95% CI 0.46 to 0.81; 7 trials, n=392), less intraventricular haemorrhage (RR 0.59, 95% CI 0.41 to 0.85; 10 trials, n=539), and lower risk for necrotising enterocolitis (RR 0.62, 95% CI 0.43 to 0.90; 5 trials, n=241) than early clamping. However, the peak bilirubin concentration was higher for infants allocated to delayed cord clamping compared with immediate clamping (mean difference 15.01 mmol/L, 95% CI 5.62 to 24.40; 7 trials, n=320). There were no clear differences in other outcomes.
Another systematic review and meta-analysis included 18 RCTs (2834 infants). Mostly the delayd of clamping was 60 seconds or more. Delayed clamping reduced hospital mortality (RR 0.68; 95% CI 0.52 to 0.90; risk difference, -0.03; 95% CI -0.05 to -0.01; P = .005; number needed to benefit, 33; 95%). Subgroup analyses showed no differences between randomized groups in Apgar scores, intubation for resuscitation, admission temperature, mechanical ventilation, intraventricular hemorrhage, brain injury, chronic lung disease, patent ductus arteriosus, necrotizing enterocolitis, late-onset sepsis, or retinopathy of prematurity. Delayed clamping increased peak hematocrit by 2.73 percentage points (95% CI 1.94 to 3.52; P < .00001) and reduced the proportion of infants having blood transfusion by 10% (95% CI 6 to 13%; P < .00001). Potential harms of delayed clamping included polycythemia and hyperbilirubinemia.