The incidence of ectopic pregnancy in Hordaland County, Norway 1976-1993.
OBJECTIVE: To gain longterm knowledge of incidence rates of ectopic pregnancy, as a basis for analysing risk factors. MATERIAL: The incidence of ectopic pregnancy was studied in the county of Hordaland, Western Norway, through 18 years, 1976-1993. The protocols of 1821 cases of ectopic pregnancy were registered. Population data of the county, the number of births and legal abortions were available. RESULTS: There was considerable increase in crude numbers of ectopic pregnancies throughout the period. Grouping the cases in three six-year periods showed an increased crude incidence rate per 100,000 women from 95 during 1976-81 to 154 during 1988-93. The corresponding rates per 1000 births increased from 13.6 to 22.2 and the rates per 1000 reported pregnancies from 11.2 to 18.0. All rates increased also in women aged 40-44 years. During the years 1979-1993 the rates per 1000 reported pregnancies increased by 25%, from 9.4 to 11.8 in age groups below 30 years, while the rates for women over 35 years increased by 98%, from 20.7 to 40.9. Compared to the age group 15-19, women over 35 years had an eightfold risk during the last period. In addition they also contributed to higher numbers of reported pregnancies by 58%. CONCLUSION: The rates of ectopic pregnancy increased in age groups older than 20 years during 1976-93, moderately in younger age groups, but considerably in older age groups, who also contributed with higher total rates of pregnancy. More older women, with presumably accumulated risk factors getting pregnant, thus explain part of the increased rates of this disease.