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

The main health risks of modern oral contraceptives (OCs) areassociated with simultaneous smoking. According to current medicalguidelines in Finland, OCs should not be prescribed for smokersaged over 30 years. We report how smoking and OC use were relatedfrom 1975 to 1993. The data were collected from 3 national postalsurveys: a biannual survey of 16 and 18 year old girls since1981 (sample sizes of 462–1,667 and response rates of83–91%), an annual survey of 20–39 year old womensince 1978 (size of 5 year age groups of 205–375 and responserates of 68–91%) and a survey of 20–39 year oldtwins in 1975 and 1981 (size of 5 year age groups of 758–3,366and response rates of 85–90%). Early initiation of OCsbecame more frequent. Half of the 16 year old and one-thirdof 18 year old OC users were smokers in the most recent survey.Adult women aged under 30 years more than doubled their OC useduring the 1980s. Although smoking showed a declining trend,the proportion of women having combined use of OCs and tobaccoincreased (up to 9–13% in the most recent surveys). Womenaged over 30 years increased their OC use in the late 1980s(10–18% in the most recent surveys). The combined useof OCs and tobacco has become more frequent both among adolescentand adult women. The lifetime duration of combined use willprobably increase without more active intervention on smokingin the family planning clinics, even among young women.