. Author manuscript; available in PMC: 2014 Jan 28.

Published in final edited form as: Biol Res Nurs. 2013 Jan 21;16(1):64–71. doi: 10.1177/1099800412471580

Table 2.

Methodological Issues that Affect the Use of Cortisol as a Biomarker of Stress in Labor and Recommendations

Plasma Cortisol Assay Selection & Use
Methodological Issues	Recommendations
Both total and free plasma levels increase Binding proteins affect free cortisol concentration High pregnancy plasma cortisol levels increase with advancing labor Labor is a random event; controlling for time of day is unfeasible	Measure free cortisol (bioactive) Analyze binding proteins CRHbp and CBG Dilute plasma samples before analysis; check upper limit of assay sensitivity Do not try to control for circadian rhythms

Data Collection with Parturients
As labor progresses psychophysiological stress increases Clinical interventions affect stress hormones and uterine contractility Cortisol is essential to maintain glucose levels when glycogen stores are depleted with fasting or with a long labor and difficult second stage	Document the point in labor for specimen collection (e.g.,1^st vs 2^nd stage); standardize measures by cervical dilation &/or interventions Document clinical interventions: Analgesia Oxytocin Other (e.g., artificial rupture of membranes, intrauterine pressure catheter) Monitor uterine contractions Document PO & IV intake prior to & during labor Document duration and number of expulsive efforts

Data Collection with Parturients

Methodological Issues

Recommendations

As labor progresses psychophysiological stress increases
Clinical interventions affect stress hormones and uterine contractility
Cortisol is essential to maintain glucose levels when glycogen stores are depleted with fasting or with a long labor and difficult second stage

Document the point in labor for specimen collection (e.g.,1^st vs 2^nd stage); standardize measures by cervical dilation &/or interventions
Document clinical interventions:
- Analgesia
- Oxytocin
- Other (e.g., artificial rupture of membranes, intrauterine pressure catheter)
Monitor uterine contractions
Document PO & IV intake prior to & during labor
Document duration and number of expulsive efforts

Study Design Selection & Measures
Methodological Issues	Recommendations
Large individual variation and type of stressor affect cortisol concentration Inconsistent results for effects of pain interventions on cortisol concentration Subjective pain, anxiety, and fear along with neuroendocrine hormones CRH, ACTH, oxytocin, vasopressin affect cortisol	Use within-subjects design Use repeated measures through 60 min postintervention to capture changes from baseline Use psychophysiological mixed methods

Note. ACTH = adrenocorticotropic hormone; CBG = corticosteroid binding globulin; CRH = corticotropin releasing hormone; CRHbp = CRH-binding protein; IV= intravenous; PO = by mouth.