Context: Pregnant tissues express corticotropin-releasing factor (CRF), a peptide modulating fetal and placental ACTH and cortisol secretion. These actions are modulated by the locally expressed CRF-binding protein (CRF-BP).

Objective: to determine if CRF, CRF-BP, ACTH, and cortisol concentrations change in amniotic fluid and umbilical cord plasma in the presence of intra-amniotic infection/inflammation (IAI) in women with spontaneous labor at term.

Design: cross-sectional study

Setting: Tertiary referral center for obstetric care

Patients: women in active labor at term with (n=39) and without (controls; n=78) IAI.

Main outcome measures: Amniotic fluid and umbilical cord plasma concentrations of CRF, CRF-BP, ACTH, and cortisol measured by radioimmuno (RIA) and immunoradiometric (IRMA) assays.

Results: In patients with IAI, amniotic fluid CRF (0.97 ± 0.18 ng/mL) and CRF-BP (33.06 ± 5.54 nmol/L) concentrations were significantly (p<0.001) higher than in controls (CRF: 0.32 ± 0.04 ng/mL; CRF-BP: 14.69 ± 2.79). The umbilical cord plasma CRF and CRF-BP concentrations were significantly (p<0.001, for all) higher in women with IAI than in controls (CRF: 2.96 ± 0.35 ng/mL vs. 0.38 ± 0.18 ng/mL; CRF-BP: 152.12 ± 5.94 nmol/L vs. 106.9 ± 5.97). In contrast, amniotic fluid and umbilical cord plasma ACTH and cortisol concentrations did not differ between groups.

Conclusions: amniotic fluid and umbilical cord plasma CRF and CRF-BP concentrations are increased in women with spontaneous labor at term and IAI. CRF-BP may modulate CRF actions on ACTH and cortisol secretion, playing a pivotal role in limiting the inflammatory process and, thus, avoiding an over activation of the fetal/placental HPA axis at birth.