Effect of delayed cord clamping on systemic blood flow: a randomized controlled trial

Objective: To determine whether delayed cord clamping improves systemic blood flow compared with immediate cord clamping in very preterm infants in the first 24 hours. Study design: Women delivering at <30 weeks' gestation at 5 tertiary centers were randomized to receive immediate cord clamping (<10 seconds) or delayed cord clamping (≥60 seconds). Echocardiography and cardiorespiratory data were collected at 3, 9, and 24 hours after birth. The primary outcome was mean lowest superior vena cava (SVC) flow. Results: Of 266 infants enrolled, 133 were randomized to immediate cord clamping and 133 to delayed cord clamping. The 2 groups were similar at baseline, including mean gestation (immediate cord clamping 28 weeks vs delayed cord clamping 28 weeks) and birth weight (immediate cord clamping 1003 g vs delayed cord clamping 1044 g). There was no significant difference between groups in the primary outcome of mean lowest SVC flow (immediate cord clamping 71.4 mL/kg/min [SD 28.1] vs delayed cord clamping 70.2 mL/kg/min [SD 26.9]; P = .7). For secondary outcomes, hemoglobin increased by 0.9 g/dL at 6 hours in the group with delayed cord clamping (95% CI 3.9, 14.4; P = .0005, adjusted for baseline). The group with delayed cord clamping had lower right ventricular output (−21.9 mL/kg/min, 95% CI −39.0, −4.7; P = .01). Rates of treated hypotension, ductus arteriosus size and shunt direction, and treatment of the ductus arteriosus were similar. Conclusions: Delayed cord clamping had no effect on systemic blood flow measured as mean lowest SVC flow in the first 24 hours in infants <30 weeks' gestation. Trial registration: Australia New Zealand Clinical Trials Registry: ACTRN12610000633088.