Maternal plasma corticotrophin-releasing factor and urocortin levels in post-term pregnancies

Corticotrophin-releasing factor (CRF) and urocortin are two placental neuropeptides that are involved in the mechanisms of labour by modulating myometrial activity. Maternal plasma levels of both CRF and urocortin are increased at term and preterm labour, whilst those of CRF are reduced in women who are destined to experience post-term delivery. The present study evaluated maternal plasma levels in term and post-term pregnancies out of labour.

A group of healthy pregnant women was enrolled and subdivided as follows: (i) at term out of labour (n = 19; 276 +/- 0.7 days of gestation; samples collected at the time of elective caesarean section due to previous uterine surgery); (ii) post-term (n = 19; 291 +/- 1.4 days of gestation), from whom samples were collected before induction of labour.

Urocortin and CRF measurements by radioimmunoassay; digital palpatory cervical examination and Bishop score computation; cervical length and funnelling presence assessment by transvaginal ultrasonography.

Maternal plasma CRF concentrations were significantly (P < 0.05) lower whilst those of urocortin were unchanged in post-term compared with term pregnancy. However, CRF and urocortin levels were both significantly (P < 0.05 and P < 0.001 respectively) higher in pregnancies delivered within 12 h of labour induction than in those that remained undelivered, and were significantly correlated with the induction-delivery interval (CRF: r = -0.676, P = 0.0015; urocortin: r = -0.783, P < 0.0001).

CRF and urocortin levels are decreased and unchanged, respectively, in post-term pregnancy when compared with term pregnancy. Both CRF and urocortin correlate with the time of labour onset after induction. Since CRF derives from the placenta, and urocortin from the fetus, the concerted expression of these neuropeptides appears to be relevant in determining the length of human gestation.