Ectopic pregnancy: incidence and review of determinant factors.

The incidence of ectopic pregnancies has been expressed in various ways that are not comparable and provide widely differing estimates due to individual definitions of the denominator. Population-based data are presented based on a count of all ectopic pregnancies reported in short stay hospitals in Maine, Rhode Island, and Vermont in 1974-1976. The incidence is 40 per 10(5) female population age 14-44 and is more consistent across 80 hospital service areas than other gynecological diagnoses. The data do not reveal an increasing incidence over these 3 years in contrast to national surveys based on a longer period of observation. A review of determinant factors for ectopic pregnancy is presented, and current theories concerning the etiology, changes in contraceptive practices, innovations in sterilization procedures, or advances in diagnosis do not appear individually or collectively to explain the increasing incidences reported by others. Further basic biologic and epidemiologic research is needed to determine causes and trends in this principal cause of first trimester mortality among pregnant women.