The risk for preterm labor in women receiving 17 alpha-hydroxyprogesterone caproate prophylaxis for preterm birth prevention.

We sought to identify maternal or clinical characteristics of women likely to develop preterm labor (PTL) at <34 weeks' gestation while receiving 17 alpha-hydroxyprogesterone caproate (17P) prophylaxis. Current singleton gestations with prior preterm delivery enrolled for outpatient 17P administration at <27 weeks' gestation were identified ( N = 1177). Maternal and clinical characteristics were compared between women hospitalized and diagnosed with PTL at <34 weeks' gestation (PTL group, N = 270) and those without PTL (No PTL group, N = 660). PTL at <34 weeks' gestation occurred in 270/1177 (22.9%) of patients receiving 17P prophylaxis (mean gestational age at diagnosis was 28.3 +/- 4.0 weeks). Recurrent preterm delivery occurred in 73.3% of women with PTL at <34 weeks. Maternal age, marital status, race, tobacco use, cerclage, gestational age at start of 17P, and Medicaid status were similar between the groups. Women developing PTL at <34 weeks were more likely to have >1 prior preterm delivery than those without PTL (35.2% versus 25.9%, P = 0.006, odds ratio [95% confidence interval] 1.5 [1.1, 2.1]). Women receiving 17P prophylaxis remain at increased risk for PTL and preterm birth. Patient education and surveillance for PTL symptoms may be warranted in women with a history of more than one prior preterm delivery. Thieme Medical Publishers.