Objective: To examine if changes in fetal plasma concentrations of cortisol or dehydroepiandrosterone sulfate (DHEAS) levels are associated with human term parturition.
Methods: Umbilical cord plasma cortisol and DHEAS concentrations were measured in 374 singleton pregnancies that delivered at term in the following six groups: group 1, cordocentesis for clinical indications before 36 weeks of gestation (n = 93); group 2, cordocentesis for clinical indications after 36 weeks of gestation (n = 9); group 3, cord blood sampling after elective cesarean section (CS) at term without labor (n = 140); group 4, cord blood sampling after CS at term with early labor (cervical dilatation < or =3 cm, n = 18); group 5, cord blood sampling after CS at term with active labor (cervical dilatation 4 cm or greater, n = 26); group 6, cord blood sampling after vaginal delivery at term (n = 88). Corticosteroids were not administered before blood collection.
Results: (1) Fetal plasma cortisol remained unchanged until 36 weeks of gestation and increased thereafter to term; (2) active labor was associated with a significant increase in fetal plasma cortisol; (3) fetal plasma DHEAS increased at term gestation (>36 weeks) but did not increase during active labor; (4) the cortisol/DHEAS ratio (stress index) increased with advancing gestation and with active labor at term. CONCLUSIONS. Human parturition at term is associated with an increase in fetal plasma cortisol and in the cortisol/DHEAS ratio, but not in DHEAS.