Maternal and umbilical cord plasma-cortisol-concentrations related to different types of deliveries.

Abstract

Maternal and cord plasma cortisol concentrations have been measured after vaginal deliveries (spontaneous and forceps) or Caesarean sections. The plasma samples were analyzed by a competitive protein binding assay before and after fractionation using Sephadex LH-20 columnchromatography. The method is described in detail. With the application of chromatography the results for the cortisol concentrations were in the maternal plasma approx. 30% and in the cord plasma approx. 70% lower than those obtained without previous plasma purification. Chromatography is thought to eliminate certain compounds from maternal and cord plasma which compete with cortisol for the binding sites on the cortisol binding globulin. Its application seems an essential methodological step in cortisol measurements. The maternal cortisol concentration is after a vaginal delivery twice as high as the prelabour values, whereas a Caesarean section is accompanied only by a moderate rise in the plasma cortisol. The cortisol level in the newborn delivered vaginally is twice to threetimes as high as that after a Caesarean section. The highest values are found in the forceps group. There is no direct correlation between the maternal and cord plasma cortisol concentrations. On the contrary it seems that the newborn is able to increase its own plasma cortisol concentration independently, e.g. in response to the stress caused by the delivery. The absence of such a stress, as in the case of a Caesarean section, results in low cord plasma cortisol levels, a fact that could be hazardous for the newborn.