OBJECTIVE To compare the frequency with which unplanned pregnancies occur in individuals with anorexia nervosa relative to women without eating disorders in the Norwegian Mother and Child Cohort Study. METHODS In a sample of 62,060 women, 62 reported anorexia nervosa. Using data from a questionnaire completed by all participating mothers, we compared mother's age at birth and the frequency with which mothers reported their index pregnancy as being unplanned. RESULTS Women with anorexia nervosa were younger (26.2 years, standard deviation 4.76) than women with no eating disorder (29.9 years, standard deviation 4.60) at the time of birth. Significantly more women with anorexia nervosa (50.0%) reported unplanned pregnancy than women in the referent group (18.9%). After adjustment for maternal age and infertility treatment, the relative risk of unplanned pregnancy in individuals with anorexia nervosa was 2.11 (95% confidence interval 1.64-2.72). Induced abortion was also significantly more common in women with anorexia nervosa than referent women (24.2% compared with 14.6%). CONCLUSIONS The higher rate of unplanned pregnancy and abortion in women with anorexia nervosa is of clinical concern because absent or irregular menstruation may be misinterpreted as decreasing risk of pregnancy. METHODS II.