Cortisol concentrations in the umbilical artery and vein of breech-presenting infants at term in relation to the method of delivery.

Umbilical cord artery and vein cortisol levels and cord artery pH were measured in 32 breech deliveries. There was no detectable increase in fetal cortisol output in relation to fetal acidosis. It is considered that elevation of fetal cortisol levels is caused by maternal transfer of this hormone transplacentally during stressful delivery rather than by enhanced fetal adrenal activity.