The long-term influence of combined oral contraceptives on body weight.

BACKGROUND There is a need to increase our knowledge regarding the influence of combined oral contraceptive (COC) use on individual weight change in the long term. The first aim of this study was to assess the long-term influence of COC's on body weight, and the second aim was to describe body weight increase during the fertile period. METHODS Postal questionnaires regarding weight/height, contraception, reproductive health, smoking and exercise were sent to random samples of 19-year-old women born in 1962 (n= 656) and 1972 (n = 780) resident in the city of Gothenburg, Sweden in 1981 and 1991. The responders were followed longitudinally, and the same women were contacted again every fifth year from 1986-2006 and from 1996-2006, respectively. RESULTS There was no significant difference in weight increase in the women grouped according to use or non-use of COC or duration of COC use. The two cohorts of women were grouped together in a longitudinal analysis and the following factors age, COC use, children, smoking and exercise were included in the model. The only predictor for weight increase was age (P < 0.001), resulting in a gain of 0.45 kg/year. There was no correlation between weight change and COC use or duration of COC use, number of children or exercise. Smokers decreased (P < 0.001) their weight by 1.64 kg per 15 years. Between 19 and 44 years of age, the 62-cohort had successively increased (P < 0.0001) their body weight/BMI by 10.6 kg/3.7. Women from the 72-cohort had a higher (P < 0.05) weight/BMI compared with women of the same age from the 62-cohort. CONCLUSIONS COC use was not found to be a predictor for weight increase in the long term. Body weight/BMI increased by 10.6 kg/3.7 between 19 and 44 years of age in a random sample of Swedish women born in 1962. Women from the 72-cohort had a greater body weight/BMI compared with the 62-cohort.