Plasma progesterone in the umbilical vessels at vaginal delivery of term infants

The influence of stress and related factors on umbilical‐cord vessel progesterone concentrations have been investigated in 150 vaginal deliveries. Cord vein progesterone levels were greater in breech deliveries than in forceps deliveries and in vaginal deliveries by maternal effort alone. Within the forceps group there was no difference in cord vessel progesterone concentrations between lift‐out, mid‐cavity or rotational forceps deliveries. Levels of progesterone were significantly greater in forceps deliveries where the infant was clinically distressed (P