497: Does Fibronectin Status Influence the Effectiveness of Sustained Tocolysis in Women with Threatened Preterm Labor?

ObjectiveTo assess the influence of fibronectin status on the effectiveness of sustained tocolysis in women with threatened preterm labor, after the initial standard 48 hours of tocolytic treatment.Study DesignThis is a secondary analysis of the APOSTEL II trial (NTR 1336) in which women who were admitted for preterm labor, but had not delivered 48 hours after initiation of tocolysis, were randomized for tocolysis (nifedipine for 12 days) or placebo. In this study, we performed blinded fibronectin tests in a subset of women with intact membranes. We compared the risk of preterm delivery in fibronectin positive and negative women by using a log-rank test and Cox regression. The influence of the fibronectin test result on the effectiveness of sustained tocolysis was assessed by using an interaction term. Women were censored when they reached term gestation (37 weeks), we adjusted for gestational age (GA) at inclusion.ResultsAmong the 406 women included in the trial, we performed a blinded fibronectin test in 93 women, of which 57 women had a negative fibronectin test and 36 a positive test. The median GA at inclusion was 29+2 (IQR 28+3 to 31+0) weeks in fibronectin negative women and 28+5 (IQR 27+3 to 30+5) weeks in positive women. The median GA at delivery of fibronectin negative women was 38+0 (IQR 35+6 to 38+6) weeks, compared to 32+5 (IQR 30+2 to 36+2) weeks in positive women (p < 0.001). Fibronectin positive women were at higher risk for preterm delivery compared to negative women at any point of time (HR 5.0 (95%CI 2.8 to 8.9). Whether women were fibronectin negative or positive did not alter the effect of sustained tocolysis on the risk of preterm delivery (p for interaction = 0.45); the hazard ratios of sustained tocolysis were comparable in these women (resp. HR 0.89 (95%CI 0.36 to 2.2) and HR 1.1 (95%CI 0.55 to 2.4)).ConclusionsAmong women who were undelivered at 48 hours after initiation of tocolysis for threatened preterm labor, fibronectin is a strong marker for the occurrence of preterm delivery. However, maintenance tocolytic therapy with nifidepine is not affective in this subgroup. ObjectiveTo assess the influence of fibronectin status on the effectiveness of sustained tocolysis in women with threatened preterm labor, after the initial standard 48 hours of tocolytic treatment. To assess the influence of fibronectin status on the effectiveness of sustained tocolysis in women with threatened preterm labor, after the initial standard 48 hours of tocolytic treatment. Study DesignThis is a secondary analysis of the APOSTEL II trial (NTR 1336) in which women who were admitted for preterm labor, but had not delivered 48 hours after initiation of tocolysis, were randomized for tocolysis (nifedipine for 12 days) or placebo. In this study, we performed blinded fibronectin tests in a subset of women with intact membranes. We compared the risk of preterm delivery in fibronectin positive and negative women by using a log-rank test and Cox regression. The influence of the fibronectin test result on the effectiveness of sustained tocolysis was assessed by using an interaction term. Women were censored when they reached term gestation (37 weeks), we adjusted for gestational age (GA) at inclusion. This is a secondary analysis of the APOSTEL II trial (NTR 1336) in which women who were admitted for preterm labor, but had not delivered 48 hours after initiation of tocolysis, were randomized for tocolysis (nifedipine for 12 days) or placebo. In this study, we performed blinded fibronectin tests in a subset of women with intact membranes. We compared the risk of preterm delivery in fibronectin positive and negative women by using a log-rank test and Cox regression. The influence of the fibronectin test result on the effectiveness of sustained tocolysis was assessed by using an interaction term. Women were censored when they reached term gestation (37 weeks), we adjusted for gestational age (GA) at inclusion. ResultsAmong the 406 women included in the trial, we performed a blinded fibronectin test in 93 women, of which 57 women had a negative fibronectin test and 36 a positive test. The median GA at inclusion was 29+2 (IQR 28+3 to 31+0) weeks in fibronectin negative women and 28+5 (IQR 27+3 to 30+5) weeks in positive women. The median GA at delivery of fibronectin negative women was 38+0 (IQR 35+6 to 38+6) weeks, compared to 32+5 (IQR 30+2 to 36+2) weeks in positive women (p < 0.001). Fibronectin positive women were at higher risk for preterm delivery compared to negative women at any point of time (HR 5.0 (95%CI 2.8 to 8.9). Whether women were fibronectin negative or positive did not alter the effect of sustained tocolysis on the risk of preterm delivery (p for interaction = 0.45); the hazard ratios of sustained tocolysis were comparable in these women (resp. HR 0.89 (95%CI 0.36 to 2.2) and HR 1.1 (95%CI 0.55 to 2.4)). Among the 406 women included in the trial, we performed a blinded fibronectin test in 93 women, of which 57 women had a negative fibronectin test and 36 a positive test. The median GA at inclusion was 29+2 (IQR 28+3 to 31+0) weeks in fibronectin negative women and 28+5 (IQR 27+3 to 30+5) weeks in positive women. The median GA at delivery of fibronectin negative women was 38+0 (IQR 35+6 to 38+6) weeks, compared to 32+5 (IQR 30+2 to 36+2) weeks in positive women (p < 0.001). Fibronectin positive women were at higher risk for preterm delivery compared to negative women at any point of time (HR 5.0 (95%CI 2.8 to 8.9). Whether women were fibronectin negative or positive did not alter the effect of sustained tocolysis on the risk of preterm delivery (p for interaction = 0.45); the hazard ratios of sustained tocolysis were comparable in these women (resp. HR 0.89 (95%CI 0.36 to 2.2) and HR 1.1 (95%CI 0.55 to 2.4)). ConclusionsAmong women who were undelivered at 48 hours after initiation of tocolysis for threatened preterm labor, fibronectin is a strong marker for the occurrence of preterm delivery. However, maintenance tocolytic therapy with nifidepine is not affective in this subgroup. Among women who were undelivered at 48 hours after initiation of tocolysis for threatened preterm labor, fibronectin is a strong marker for the occurrence of preterm delivery. However, maintenance tocolytic therapy with nifidepine is not affective in this subgroup.