Long-term contraceptive effect of injectable progestogens: inhibition and reestabilishment of fertility.

Abstract

The antifertility effect of long-acting injectable progestogens was evaluated in 2,000 young, fertile women observed during 34,800 woman-months. Depo-medroxyprogesterone (Depo-MPA) was injected intramuscularly every 6 months in 1,580 women. The compound was used at different dosages, for a total of 30,900 months. There was a total incidence of 2.72 pregnancies per 100 woman-years. Injectable chlormadinone acetate was given every 3 months, 100 mg intramuscularly. This dosage seemed inadequate, since a total of 25.5 pregnancies per 100 woman-years occurred in 1600 months observations. Injectable norethisterone enanthate, 200 mg, was administered to 130 women every 3 months. In 2300 months of observation, there was a total incidence of 9.4 pregnancies per 100 woman-years. In most subjects, fertilization occurred promptly upon abandoning the method; however, from 7 to 18 months were required when depo-mpa was used. In subjects wishing to become pregnant sooner, ovulation was induced with clomiphene citrate and human chorionic gonadotropin. Histologic and histochemical observations in ovarian tissue obtained by biopsy demonstrated development of follicles up to the graafian stage.