Objective: To evaluate oral micronized progesterone (OMP) to prevent preterm birth (PTB).
Methods: A randomized, double-blind, placebo-controlled trial of 150 women with at least one PTB who received 100 mg of OMP or placebo twice a day from recruitment (18-24 weeks) until 36 weeks or delivery.
Results: PTB occurred in 29 (39.2%) women in the OMP group (n=74) compared with 44 (59.5%) in the control group (n=74, P=0.002). Mean gestational age at delivery was higher in the OMP group (36.1 vs 34.0 weeks, P<0.001). Fewer preterm births occurred between 28 and 31 weeks plus 6 days in the OMP group (RR 0.20; 95% CI, 0.05-0.73, P<0.001). Neonatal age at delivery (34 vs 32 weeks, P<0.001), birth weight (2400 vs 1890 g, P<0.001), NICU stay (>24 h, P<0.001), and Apgar scores (P<0.001) were more favorable in the OMP group, and fewer neonatal deaths occurred (3 vs 7, P=0.190).
Conclusion: OMP reduced the risk of PTB between 28 and 31 weeks plus 6 days, NICU admissions, and neonatal morbidity and mortality in high risk patients.