In a recent study doppler ultrasound was used to measure arterial and venous umbilical blood flow during delayed cord clamping in term vaginal deliveries. After birth, the probe was placed in the middle of the umbilical cord and pattern and duration of flow in vein and arteries were evaluated until cord clamping. In 90% of infants, umbilical venous flow was still present at 4 minutes and 36 seconds. In 83% of infants, umbilical arterial flow was still present at 4 minutes and 22 seconds and in 72% of infants bidirectional arterial flow was observed. Bidirectional arterial flow appeared at 45 seconds after birth and persisted for a median duration of 2 minutes and 24 seconds (01:37- 03:52). This study implies that placental gas exchange may remain active for at least 4-5 minutes after birth and suggests that delaying cord clamping for 4-5 minutes while initiating resuscitation may be feasible.