Oral contraception and smoking - Time trends for a risk behaviour in Finland

The main health risks of modern oral contraceptives (OCs) are associated with simultaneous smoking, According to current medical guidelines in Finland, OCs should not be prescribed for smokers aged over 30 years, We report: how smoking and OC use were related from 1975 to 1993. The data were collected from 3 national postal surveys: a biannual survey of 16 and 18 year old girls since 1981 (sample sizes of 462-1,667 and response rates of 83-91%), an annual survey of 20-39 year old women since 1978 (size of 5 year age groups of 205-375 and response rates of 68-91%) and a survey of 20-39 year old twins in 1975 and 1981 (size of 5 year age groups of 758-3,366 and response rates of 85-90%), Early initiation of OCs became more frequent, Half of the 16 year old and one-third of 18 year old OC users were smokers in the most recent survey, Adult women aged under 30 years more than doubled their OC use during the 1980s. Although smoking showed a declining trend, the proportion of women having combined use of OCs and tobacco increased (up to 9-13% in the most recent surveys). Women aged over 30 years increased their OC use in the late 1980s (10-18% in the most recent surveys), The combined use of OCs and tobacco has become more frequent both among adolescent and adult women, The lifetime duration of combined use will probably increase without more active intervention on smoking in the family planning clinics, even among young women.