Can Progesterone Prevent Preterm Birth?

Progesterone is necessary to maintain pregnancy, in part because it inhibits uterine contractility. Studies in some animal models indicate that progesterone levels fall markedly before onset of labor, and 17 alpha-hydroxyprogesterone acetate (17P) has been shown to reduce the rate of recurrent preterm birth (Journal Watch Jun 24 2003). Two new multisite randomized double-blind trials address the efficacy of progesterone in women at increased risk for preterm labor.

In the first study, 655 women with twin gestations received weekly intramuscular injections of 17P or placebo beginning at 16 to 20 weeks of gestation and ending at 35 weeks. Delivery or fetal death before 35 weeks was not significantly different in the two groups.

In the second st…