Incidence of ectopic pregnancy in Rochester, Minnesota, 1950-1981.

Trends in the occurrence of ectopic pregnancy from 1950 through 1981 were evaluated in the defined population of Rochester, Minnesota. The average ratio of ectopic pregnancies to live births was 1:171. The ratio declined from 1:141 to 1:217 from 1955-1959 to 1970-1974 and increased sharply to 1:122 by 1975-1980. Similarly, the average age-adjusted incidence rate of ectopic pregnancies per 100,000 women of childbearing age was 49 over the period studied. A peak rate of 79 per 100,000 was reached in 1955 to 1959, and a trough of 30 per 100,000 occurred in 1970 to 1974; this was followed by a sharp increase to 49 per 100,000 in 1975 to 1981. Methods of measuring ectopic pregnancy are contrasted, and possible risk factors are suggested.