Low-dose progestogens and ectopic pregnancy. (Letter)

A commentary on the results reported previously of a higher relative risk for the progestogens D-norgestrel and norethisterone in developing an ectopic pregnancy as compared with lynestrenol questions the characteristics of the group studied. It is pointed out that the incidence of ectopic pregnancy for these 3 closely related 19-norsteroids is more pronounced than their relative contraceptive efficiency as indicated by the Pearl Index figures quoted in the original communication. The inquiry has included such questions as: 1) the form of the hormone administered 2) were members of the study from the same ethnic group 3) were the subjects of the same stature and weight 4) were the women married and able to have unrestricted intercourse and 5) were they of proven fertility. The results reported indicate a disparity of action between 3 closely related steroids. It is implied that lynestrenol has an efficient action on the cervical mucus and that the other 2 compounds achieve their action by means of the endometrium.