Fertility inhibition by an injectable progestogen acting for 3 months. A clinical survey of 130 fertile women treated with norethisterone enanthate.

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Intramuscular injections of an oily suspension of 200 mg of norethisterone enanthate were given to 130 young fertile healthy women at 3-month intervals; most were treated for more than a year with the average 17.6 months. 46 began the injections within 30 days postpartum. Physical and pelvic examinations and a Papanicolaou smear were performed at the beginning and repeated every 12 months. Amenorrhea or irregular uterine bleeding were the most troublesome side effects and the most frequent cause for the 25% dropout rate. Accessory oral estrogens were added for 5-7 days of each month to relieve these symptoms. On a selected group vaginal cytology cervical mucus and Huhner-Sims postcoital tests were done along with an endometrial biopsy and urinary pregnanediol excretion studies. Changes in cervical mucus interfering with sperm survival and ascent were noted. The endometrial histology was normal in 17 biopsies with iatrogenic changes in 64 specimens. There were 3 pregnancies 2.3% in 2300 treated months. No major changes were observed in libido or orgasm. The inhibition of fertility is rapidly reversible upon discontinuing therapy. In 5 or 6 women undergoing laparotomy while in therapy no signs of ovulation or corpus luteum formation were found. In one operated on during the fourth month after the last injection a recent corpus luteum was found.