Relaxin levels in antenatal patients following in vitro fertilization.

The aim of this study was to investigate the relationship between serum relaxin and pregnancy outcome in a group of patients pregnant after in vitro fertilization (IVF). Patients who delivered a single live infant at term after IVF had mean serum levels of relaxin more than double the mean levels in normal antenatal patients. The high relaxin levels were compatible with delivery at term. However, because of the proposed role of relaxin in the process of cervical ripening, the high serum levels may help explain the high rate of preterm labor observed among IVF patients.