Correlations between stress hormone levels in umbilical cord blood and duration of delivery.

Correlations between umbilical cord blood concentration of stress response hormone cortisol and prolactin, and delivery duration were examined. Thirty-three cases were selected in which both mothers and neonates were healthy, and the neonates were delivered at full term. The umbilical cord blood was collected at the time of delivery and concentrations of cortisol and prolactin were measured. The cortisol level was significantly higher after vacuum-assisted delivery than after spontaneous delivery (p=0.044). Significant positive correlations (p=0.0289) were observed between cortisol level and delivery duration. In particular, the duration of the second stage of delivery showed stronger positive correlation (p=0.0304) with the cortisol level. The prolactin level showed weak correlation with the duration of full delivery and the second stage of delivery. The findings suggest that foetuses may respond to stress by uterine contraction during delivery.