Progesterone,16a-Hydroxy-Progesterone,and Maintenance of Pregnancy In Mice. ∗

Summary

In the Hooker-Forbes bio-assay in CHI mice, the minimal effective dose of 16a-hydroxy-progesterone was 0.006 μg. Subcutaneous pellets of this compound did not affect the normal duration of pregnancy or survival of fetuses in intact mice. In mice implanted with 2 progesterone pellets (about 18 mg) of pure progesterone on day 12 of pregnancy and ovariectomized on day 14, fetal survival was good. If pellets of 16a-hydroxy-progesterone were substituted, total abortion promptly occurred. If the pellets were a mixture of 16a-hydroxy-progesterone and progesterone, some fetuses survived, the survival rate diminishing as the proportion of 16a-hy-droxy-protesterone to a fixed amount (about 18 mg) of progesterone increased.