Ethinyl oestradiol plus dl-norgestrel or levonorgestrel in the Yuzpe method for post-coital contraception: results of an observational study.

This observational study compares the efficacy and incidence of side-effects between dl-norgestrel (2 mg) and levonorgestrel (1 mg) associated with ethinyl oestradiol (200 micrograms) given in two doses 12 h apart for emergency post-coital contraception. A total of 117 consecutive women were given dl-norgestrel in combination with the oestrogen (dl-norgestrel group) while 423 consecutive subjects received the combination ethinyl oestradiol/levonorgestrel (levonorgestrel group). Overall, four (0.8%) pregnancies occurred in the 540 treated women, one (0.9%) in the dl-norgestrel group and three (0.7%) in the levonorgestrel group. In addition to this similar high contraceptive efficacy between both study groups, women in the levonorgestrel group had a significantly lower incidence of side-effects (23.5%) and better timing of the next menstruation after treatment (75% had bleeding on time) than those in the dl-norgestrel group (corresponding figures were 50.5 and 62.6% respectively). It is concluded that levonorgestrel should be used in preference to dl-norgestrel for post-coital contraception in the Yuzpe regimen.