The impact of maternal body mass on the effectiveness of 17 alpha-hydroxyprogesterone caproate.

Objective: To examine the impact of maternal prepregnancy body mass index (BMI) on rates of recurrent preterm delivery (PTD) in women receiving 17alpha-hydroxyprogesterone caproate (17P) prophylaxis.

Study Design: The study population was identified from a large perinatal database containing prospectively collected information from women at high risk for PTD. We included patients with a current singleton pregnancy and a history of PTD who received weekly nursing visits and 17P 250 mg intramuscular injections beginning at 16.0 to 20.9 weeks' gestation. The data were stratified by number of prior PTDs (1 or >1) and maternal prepregnancy BMI (lean, normal, overweight and obese). Primary study outcomes included the rates of recurrent PTD at <35 and 32 weeks' gestation, and pregnancy loss at <24 weeks' gestation.

Results: Delivery outcomes for 606 women receiving 17P were analyzed. There were no significant differences found in the incidence of preterm labor, the rates of recurrent PTD or pregnancy loss at <35, 32 or 24 weeks between the BMI groups.

Conclusion: Maternal prepregnancy BMI does not appear to influence the rates of recurrent PTD in women with singleton gestation receiving 17P prophylaxis. Larger studies are needed to confirm our findings.