Gestational age at initiation of 17-hydroxyprogesterone caproate (17P) and recurrent preterm delivery.

Objective: To compare rates of recurrent preterm birth between women starting treatment with 17alpha-hydroxyprogesterone caproate (17P) at 16-20.9 weeks of gestation versus 21-26.9 weeks.

Methods: Women enrolled in an outpatient program of education, nursing assessment and weekly 17P injections beginning at 16-26.9 weeks were eligible. Included were patients with singleton pregnancies and a history of preterm delivery (PTD). Pregnancy outcome was compared between women starting 17P at 16-20.9 weeks (n=156) and those starting 17P at 21-26.9 weeks (n=119) using Fisher's exact and Mann-Whitney U test statistics (p<0.05 considered significant).

Results: Mean gestational age at delivery (36.8 +/- 3.0 vs. 36.7 +/- 2.5) and rates of PTD at <37 weeks (40.4% vs. 48.7%), <35 weeks (16.7% vs. 16.8%) and <32 weeks (5.1% vs. 5.0%) were similar between the groups; all p > 0.05.

Conclusions: Rates of preterm delivery were similar in patients initiating 17P at 16-20.9 or 21-26.9 weeks. A larger sample size is warranted in order to confirm our findings.