Please cite this paper as: Easter A, Treasure J, Micali N. Fertility and prenatal attitudes towards pregnancy in women with eating disorders: results from the Avon Longitudinal Study of Parents and Children. BJOG 2011;118:1491–1498.Objective  To study the effects of eating disorders (EDs) on fertility and attitudes to pregnancy.Design  A longitudinal prospective birth cohort.Setting  Avon area, UK.Sample  A cohort of 14 663 women who enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC). Singleton and live births were included across four groups of women: lifetime anorexia nervosa (AN; n = 171); lifetime bulimia nervosa (BN; n = 199), lifetime anorexia nervosa and bulimia nervosa (AN + BN; n = 82); and the general population (n = 10 636).Methods  Fertility problems, conception time and attitudes to pregnancy were investigated in women with AN, BN and AN + BN, compared with the remaining sample (general population).Main outcome measures  Having seen a doctor for fertility problems, time taken to conceive (>12 months, and >6 months), unplanned pregnancies, and attitudes to pregnancy at 12 and 18 weeks of gestation.Results  Women with AN (OR 1.6, 95% CI 1.1–2.5; P < 0.021) and women with AN + BN (OR 1.9, 95% CI 1.1–3.4; P < 0.020) were more likely to have seen a doctor for lifetime fertility problems, and women with AN + BN were also more likely to take longer than 6 months to conceive (OR 1.9, 95% CI 1.0–3.5; P < 0.04), and to have conceived the current pregnancy with fertility treatment. Unplanned pregnancies were more common in the AN group compared with the general population. All ED groups more frequently experienced negative feelings upon discovering their pregnancy, which remained higher in the AN + BN group at 18 weeks of gestation.Conclusions  Lifetime EDs are associated with fertility problems, unplanned pregnancies and negative attitudes to pregnancy. Health professionals should be aware of EDs when assessing fertility and providing treatment for this.