Objective To determine whether high serum relaxin concentrations in the 30th week of pregnancy were associated with preterm labour.
Design Case-control study.
Setting Two antenal clinics of the Department of Obstetrics and Gynecology University Hospital of Aarhus.
Subjects A cohort of 991 women (82% of 1203 eligible) in the 30th week of pregnancy attending one of the two antenatal clinics. The cases comprised 23 (2.4%) women without pre-eclampsia or small for gestational age babies, who were delivered spontaneously before 37 completed weeks gestation. The control group of 46 women was randomly selected from the rest of the cohort, all of them were delivered at term.
Interventions Blood samples were collected at 30 weeks gestation and stored for analysis.
Main outcome measures Serum relaxin concentrations estimated by ELISA technique, length of gestation at delivery.
Results The mean serum relaxin concentrations in the 30th week of pregnancy was 455 (SD 169) pg/ml and 327 (SD 139) pg/ml in the cases and controls, respectively (P = 0003, t test). In women with preterm delivery a negative correlation was found between relaxin concentration in the 30th week of pregnancy and the gestational age at parturition (r=−0.53, P= 0.02).
Conclusion High relaxin concentrations may be associated with preterm delivery but the present results need confirmation in large scale studies.