[Experiences with levonorgestrel in postcoital contraception]

To examine levonorgestrel as a postcoital contraceptive, 77 women received an oral dose of 0.4 mg per coitus for 1011 cycles and 27 women were administered 0.75 mg per coitus for 226 cycles. In the first dose group seven women became pregnant (Pearl's index 8.3), while two pregnancies resulted in the second group, one of the latter because of faulty drug intake (uncorrected Pearl's index 10.6; corrected Pearl's index 5.3). Menstrual irregularities (chiefly break-through bleedings and oligomenorrhea) were observed in 84.4% and 88.9% of the women, respectively. The number of cycle disorders increased with increasing intake rate and diminished when the drug was applied in excess of six months. The experiments undertaken to test the mechanisms of action indicated an influence on both cervical factor and endometrium, whereas the occurrence of LH-peaks and biphasic basal body temperature patterns suggested the presence of ovulations. Application of levonorgestrel for postcoital contraception failed to be a reliable routine method of hormonal contraception because of insufficient efficacy and considerable menstrual irregularities. The drug should be administered only after unprotected sexual intercourse as might happen, to women with very low frequency of intercourse, or in periods of reduced fertility.