RESUMEN
OBJECTIVE: The aim of this study is to identify a subset of women presenting with preterm labor not responding upon tocolytic therapy, eventually resulting in preterm birth. STUDY DESIGN: The maternal admission characteristics of 185 women with preterm labor receiving tocolysis were analysed for risk factors that could predict which women will deliver within 48 h after the start of tocolysis, or before 34 weeks gestation. Univariate analysis and multivariate logistic regression analysis was performed. RESULTS: Logistic regression analysis identified the following risk factors for delivery within 48 h after the start of tocolysis: cervical dilatation at admission (odds ratio (OR, cm(-1)) 1.47; 95% confidence interval (CI), 1.44-1.49), elevated leukocyte count at admission (per 10(3) leukocytes/mm(3)) (OR 1.27; 95% CI, 1.26-1.28), use of nifedipine (OR 0.49; 95% CI, 0.26-0.49), and developing signs suggestive of chorioamnionitis following admission (OR 2.12; 95% CI, 1.04-4.33). For delivery before 34 weeks of gestation the following risk factors were identified: use of steroids (OR 5.87; 95% CI, 2.34-14.7), use of nifedipine (OR 0.46; 95% CI, 0.27-0.85), developing signs suggestive of chorioamnionitis following admission (OR 10.6; 95% CI, 3.1-35.9), and preterm premature rupture of the membranes (OR 12; 95% CI, 4.1-35.2). CONCLUSIONS: Risk factors associated for delivery within 48 h after starting tocolysis are: cervical dilatation at admission, elevated leukocyte count at admission, and developing signs suggestive of chorioamnionitis following admission. Use of nifedipine was associated with a delay of delivery >48 h. Risk factors associated for delivery within 34 weeks gestation are: use of steroids, developing signs suggestive of chorioamnionitis following admission, and ruptured membranes. Use of nifedipine was associated with a delay >34 weeks.