Relationships of cortisol, perceived stress, genitourinary infections, and fetal fibronectin to gestational age at birth.

The authors investigated the role of stress and cortisol with patients having preterm labor (PTL) and preterm birth (PTB). The relationships of maternal cortisol, perceived stress, fetal fibronectin (fFN), and genitourinary infections to PTL and PTB were studied. A prospective, longitudinal, observational study (n = 78) was conducted in a private practice in central Texas. Subjects had 4 blood draws for cortisol measurements grouped by 15-19, 20-22, 23-26, 27-30, and 31-35 weeks of gestation. Subjects had 2 vaginal swabs forfFN, chlamydia, and bacterial vaginosis screens at 23-26 and 27-30 weeks with assessment of psychosocial stress at 23-26 and 31-35 weeks. Statistical analysis was by analysis of variance, Pearson correlations, Fisher exact test, and logistic regression. There were no significant differences between the PTB, PTL, and term groups on cortisol levels at any of the gestational periods. Cortisol concentrations at any gestational stage did not correlate with gestational age at birth. A relationship of cortisol to race was observed when comparing Caucasians to other ethnic groups. A correlation (r = 0.42, P < 0.001) between the change in Perceived Stress Scale (PSS) score and gestational age was observed. The greater the decrease in PSS scores, the longer was the gestational age. A significant increase in cortisol at 19-21 weeks (P < 0.04), 23-26 weeks (P < 0.05), and 31-35 weeks (P < 0.01) was observed in patients having genitourinary infection. PTL was also significantly increased in subjects having positive genitourinary infections at either 23-26 weeks or 27-30 weeks (P < 0.01). The sensitivity of fFN to predict PTL collected at 27-30 weeks was 40%, specificity 86%, positive predictive value 55%, and negative predictive value 83%. These results indicate that cortisol is a poor predictor of either PTL or PTB. A decrease in perceived stress during the 2nd trimester was associated with an increase in length of gestation, suggesting the possibility of stress reduction as an appropriate intervention for lengthening gestational age.