Prophylaxis with 17 alpha-hydroxyprogesterone caproate for prevention of recurrent preterm delivery: does gestational age at initiation of treatment matter?

OBJECTIVE: The purpose of this study was to determine effectiveness of 17 alpha-hydroxyprogesterone caproate ( 17 P) prophylaxis by gestational age (GA) at 17 P initiation. STUDY DESIGN: Singleton gestations with >= 1 preterm birth (PTB) treated with 17 P prophylaxis for recurrent preterm birth before 27 weeks were identified from a data base. Data were stratified by GA at 17 P initiation (16-20.9 [n = 599] weeks and 21-26.9 [n = 307] weeks) and number of PTB ( 1, 2, > 2). Outcome variables were PTB at < 37, < 35, and < 32 weeks. RESULTS: No significant differences were found in gestational age at delivery or rates of recurrent PTB < 37, < 35, and < 32 weeks between those women initiating 17 P at 16-20.9 weeks or 21-26.9 weeks, or when stratified by number of prior preterm deliveries. CONCLUSION: Initiation of 17 P prophylaxis at 21-26.9 weeks is as effective as initiation at 16-20.9 weeks of gestation.