Physiological and psychological stress responses to labor and delivery as expressed by salivary cortisol: a prospective study

BACKGROUND: Labor is considered a stressful event, yet no study has described the course of stress measured by cortisol during labor and postpartum. OBJECTIVE: The objective of the study was to describe the patterns of physiological and psychological stress during labor as measured by salivary cortisol concentrations and stress questionnaires and their correlation to obstetric and neonatal outcomes. STUDY DESIGN: This prospective, observational study included 167 women with low-risk, singleton, term deliveries at a tertiary academic center. Physiological stress was evaluated by salivary cortisol measurements and emotional stress by questionnaire (stress scale ranging from 0 to 10) during the latent phase, active phase, and full dilation stages of labor as well as 2 minutes, 2 hours, and 24 hours after delivery. Cord blood cortisol and pH were also obtained. Modes of delivery, complications during labor and delivery, and early neonatal outcomes were evaluated. RESULTS: Salivary cortisol concentrations increased gradually from latent phase to active phase. The maximum increase was observed within 2 minutes of the delivery (from an average of 1.06 mu g/dL to 1.67 mu g/dL; 57% increase). Within 2 hours after delivery, cortisol decreased and reached a nongravid concentration after 24 hours (0.16 mu g/dL). Cortisol concentrations during labor and up to 2 hours postpartum were above the average concentration of nongravid women (0.5 mu g/dL). Women with epidural anesthesia had lower cortisol concentrations at complete dilation (P = .026) and 2 hours postpartum (P = .016) compared with women without epidural. Psychological stress peaked during latent and full dilation phases (mean 4.56 and 4.29, respectively). Maximum decrease from 4.29 to 2.04 (52%) occurred immediately postpartum. Cord cortisol was higher among women delivered by vacuum extraction compared with spontaneous vaginal delivery (17 +/- 2 vs 11 +/- 3.8, P = .03). CONCLUSION: This study reveals the course of cortisol concentrations during labor for low-risk pregnancies, with maximum increase immediately postpartum. Subjective stress levels decreased over the course of labor. Salivary cortisol portrays stress during labor and may be used as a reference to evaluate complicated pregnancies and to evaluate the role of cortisol during these deliveries.