“Progesterone may have an inhibitory effect on preterm cervical ripening processes, thus decreasing the risk of preterm delivery, but … once the pathologic processes of preterm labor begin, progesterone treatment is no longer effective,” the authors conclude.
Dr. Patrick Rozenberg, at the Centre hospitalier Poissy-Saint-Germain, in Poissy, and colleagues note that women who have a short cervix and who have had preterm labor arrested by tocolysis are at high risk for preterm delivery. The team conducted a trial to see if this risk can be reduced with the use of 17 alpha-hydroxyprogesterone caproate (17P).
Specifically, 188 such women in preterm labor at 24-31 weeks’ gestation underwent successful tocolysis with nifedipine, nicardipine or salbutamol and were randomly assigned to receive 500 mg of intramuscular 17P, repeated twice a week until 36 weeks or preterm delivery (whichever occurred first), or to a control group that received no treatment with 17P.
The primary outcome was time from randomization to delivery. On intent-to-treat analysis, the median time to delivery was 64 days in the 17P group and 67 days in the control group. “After adjustment for gestational age at randomization, the 17P group showed a non-significant average prolongation of pregnancy of 2 days,” the authors report.
Secondary outcomes, such as likelihood of delivery within 7 days, repeat tocolysis, or cesarean delivery were similar in both groups, Dr. Rozenberg and colleagues found.
“Therefore, 17P does not appear to be useful after arrested preterm labor,” they conclude. “As we performed a multicenter pragmatic trial, we think that this finding can be generalized to many other practice settings,” they add.
Am J Obstet Gynecol 2011.