Norepinephrine, adrenocorticotropin, cortisol and beta-endorphin in women suffering from fear of labor: responses to the cold pressor test during and after pregnancy.

BACKGROUND: Women suffering from fear of labor have reduced pain tolerance during a cold pressor test (CPT) during and after pregnancy.
METHODS: We compared levels of norepinephrine, adrenocorticotropin (ACTH), cortisol and beta-endorphin before and during the CPT up to 60 min in 20 normotensive women with and 20 without fear of labor at 37.4 +/- 0.2 (mean +/- SE) gestational weeks and at 41.9 +/- 1.6 weeks after delivery.
RESULTS: Baseline levels of norepinephrine in the pregnant fear group (1.63 +/- 0.18 nmol/L) were higher (p = 0.068) than in controls (1.38 +/- 0.14 nmol/L) but after delivery they were lower in the fear group (1.75 +/- 0.31 nmol/L vs. 2.31 +/- 0.26 nmol/L, p = 0.064). ACTH, cortisol and beta-endorphin did not differ between pregnant and nonpregnant groups. The CPT caused a 28.4% smaller response in norepinephrine in the pregnant fearful women than in controls, whereas the responses of ACTH and beta-endorphin were similar between groups during and after pregnancy. The CPT caused no significant response in cortisol. Pregnant fearful women had higher diastolic blood pressure (85.6 +/- 4.5 mmHg, mean +/- SE) than the controls (74.9 +/- 3.4 mmHg, p = 0.065).
CONCLUSIONS: Women with fear of labor were characterized by changes in norepinephrine but not in ACTH, cortisol or beta-endorphin before and during the CPT, indicating a normal pituitary-adrenal axis function.