Effectiveness of Progestogens as Maintenance Tocolysis and Urogenital Cultures: Secondary Analysis of the PROTECT Trial.

 In a recently published multicenter randomized controlled trial, we demonstrated that progestogens are not effective as maintenance tocolysis.  This study was aimed to evaluate if previous finding may be affected by positive urine culture and/or vaginal swab.  We performed a secondary analysis of the PROTECT trial (NCT01178788). Women with singleton pregnancy between 22 and 31 weeks' gestation, admitted for threatened preterm labor were considered. At admission, we collected urine culture and vaginal swabs. At discharge, women with a cervical length ≤25 mm were randomized to vaginal progesterone or 17α-hydroxyprogesterone caproate or observation group. We used Chi-square statistics, considering 97.5% CI (confidence interval) and -value less than 0.025 for significance.  Urine culture and vaginal swabs were collected in 232 out of 235 patients included in the primary analysis. Overall, 31 out of 232 women (13.4%) had positive urine culture and 60 out of 232 (25.9%) had positive vaginal swab. In women with negative urine culture, a higher rate of preterm birth was found in vaginal progesterone group (27/69, 39.7%) respect with controls (14/68, 20.6%; relative risk [RR] = 1.90; 97.5% CI: 1.01-3.57;  = 0.018).  Among women with negative urine culture, the rate of preterm birth <37 weeks' gestation was significantly increased in those receiving vaginal progesterone, reinforcing our previous findings in symptomatic women.