UN-BOUND CORTISOL IN UMBILICAL-CORD PLASMA AND MATERNAL PLASMA - REINVESTIGATION

Unbound cortisol was assayed in maternal and cord plasma. A method was used in which experimental conditions are carefully selected to approach as closely as possible the in vivo situation.* * Robin, P., Predine, J., and Milgrom, E.: J. Clin. Endocrinol. Metab. 46:277, 1978. In maternal plasma at term, the proportion of unbound cortisol (9.7 ± 1.5%) (mean ± SE) was identical to that of normal nonpregnant women (9.7 ± 0.4%). However, the concentration of unbound cortisol was 3-fold higher at term (46.0 ± 5.9 ng/ml) than that in nonpregnant women (14.2 ± 1.0 ng/ml). During labor an increase was observed, and at birth the proportion (and concentration) of unbound cortisol was extremely high varying between 17.0 ± 0.8% (92.3 ± 7.4 ng/ml) and 20.9 ± 1.4% (130.4 ± 17.9 ng/ml) (spontaneous and induced vaginal deliveries, respectively). In cord plasma at term and before labor (fetuses delivered by elective cesarean section), the proportion of unbound cortisol was high (29.1 ± 1.3 %) but its concentration (9.6 ± 1.1 ng/ml) was only slightly lower than that observed in normal adults. Labor had an important stimulatory effect as observed in cases of vaginal delivery after spontaneous labor (proportion of unbound cortisol 35.1 ± 1.2%, concentration of unbound cortisol 15.4 ± 1.35 ng/ml, respectively). No difference was observed between spontaneous and provoked labor since similarly high values of unbound cortisol were found in cord plasma after oxytocin-induced labor followed by vaginal delivery (36.2 ± 1.4% and 23.0 ± 5.2 ng/ml). © 1979.