Objective To determine if timing of cord clamping affects blood flow in the upper body, as measured by flow in the superior vena cava (SVC).

Design Observational study.

Setting Neonatal Unit, Middlemore Hospital, Auckland, New Zealand.

Patients 30 preterm infants <30 weeks' gestational age.

Intervention Cord clamping was immediate in 17 infants and delayed by 30–45 s in 13.

Results Infants in the two groups did not differ significantly in terms of gestational age, gender or use of antenatal steroids. Median flow in the SVC in the first 24 h was significantly higher in the group with delayed clamping (median 91 ml/kg/min; IQR 81–101) compared with 52 ml/kg/min (IQR 42–100) in the immediate clamping group (p=0.028). Fewer infants in the delayed group had low flow (1 compared with 9; p=0.017). All three infants with intraventricular haemorrhage (IVH) (of any grade) had low flow.

Conclusions Blood flow in the SVC was higher in infants where delayed cord clamping was performed. The relationship of IVH, low flow and timing of cord clamping requires further study.