The effect of labour on prolactin and cortisol concentrations in the mother and the fetus.

Concentrations of prolactin and cortisol were determined in maternal and umbilical cord serum of women delivered by elective Caesarean section and by vaginal delivery. There was no difference in the concentration of prolactin in the two groups of women. Similarly, cord blood prolactin concentrations were not significantly different in the two groups. Cortisol concentrations in the women undergoing Caesarean section were similar to the vaginal delivery group before the onset of labour. However, there was a significant increase in cortisol concentration at delivery following labour. The cord blood cortisol concentration was significantly higher in the neonates delivered vaginally, and it correlated with the maternal cortisol concentration at delivery. The relevance of these findings is discussed.