Objective To compare the frequency with which unplanned pregnancies occur in individuals with anorexia nervosa (AN) relative to women without eating disorders in the large Norwegian Mother and Child Cohort Study. Method In a sample of 62,060 women, 62 reported AN. 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 AN women were younger (26.2 years; SD=4.76) than women with no eating disorder (29.9 years; SD=4.60) at the time of birth. Significantly more women with AN (50.0%) reported unplanned pregnancy than women in the referent group (18.9%). After adjustment for maternal age and infertility treatment, the relative risk (RR) of unplanned pregnancy in individuals with AN was 2.11 (95% confidence interval [CI]=1.64–2.72). Induced abortion was also significantly more common in women with AN than referent women (24.2% versus 14.6%). Conclusion The higher rate of unplanned pregnancy and abortion in women with AN is of clinical concern as absent or irregular menstruation may be misinterpreted as decreasing risk of pregnancy.