Association between raised serum relaxin levels during the eighteenth gestational week and very preterm delivery

OBJECTIVE: Our aim was to evaluate a possible association between serum rel axin levels in the 18th gestational week and preterm delivery. STUDY DESIGN: We conducted a nested case-control study that was based on se rum samples obtained in the 18th week of gestation from 1545 unselected hea lthy primiparous women. Eleven case subjects were delivered very early (9 s pontaneously, 2 by indicated cesarean delivery) and 42 moderately early (41 spontaneously, 1 by indicated cesarean delivery); 123 control subjects (12 1 having spontaneous labor, 2 undergoing indicated cesarean delivery) were randomly selected among the women with delivery at term. RESULTS: The serum relaxin concentration during the 18th gestational week w as 63% higher among subjects with very preterm deliveries than among contro l subjects (P = .01, Mann-Whitney test). High relaxin levels during the 18t h gestational week were associated with an increased risk of very preterm d elivery (odds ratio, 11.3; 95% confidence interval, 2.14-59.1) and spontane ous very preterm delivery (odds ratio, 5.5; 95% confidence interval, 1.3-23 ). There was a negative correlation for case subjects and control subjects between serum relaxin concentrations during the 18th gestational week and g estational age at delivery (P < .05). CONCLUSION: Serum relaxin may be an independent predictor when identificati on of women at risk of very preterm delivery is attempted in the 18th gesta tional week.