Cortisol levels in fetal scalp, maternal, and umbilical cord plasma.

The purpose of this study was to investigate cortisol levels in the fetal circulation prior to delivery. Fetal scalp plasma cortisol levels during labor were significantly lower than those in maternal peripheral plasma but significantly higher than those in cord plasma at delivery. Cortisol levels in fetal scalp plasma did not correlate significantly with those in either maternal or cord plasma. The greater cortisol concentrations in fetal scalp plasma relative to those in cord plasma could have been transient increases caused by fetal adrenal response to the stress of the scalp sampling procedure. There was a significant correlation between cortisol levels in maternal and cord plasma, which may mean that a considerable part of the cortisol in the fetal circulation at delivery is of maternal origin.