We explored the course of broadly defined eating disorders during pregnancy in the Norwegian Mother and Child Cohort Study (MoBa) at the Norwegian Institute of Public Health.

A total of 41 157 pregnant women, enrolled at approximately 18 weeks' gestation, had valid data from the Norwegian Medical Birth Registry. We collected questionnaire-based diagnostic information on broadly defined anorexia nervosa (AN), and bulimia nervosa (BN), and eating disorders not otherwise specified (EDNOS). EDNOS subtypes included binge eating disorder (BED) and recurrent self-induced purging in the absence of binge eating (EDNOS-P). We explored rates of remission, continuation and incidence of BN, BED and EDNOS-P during pregnancy.

Prepregnancy prevalence estimates were 0·1% for AN, 0·7% for BN, 3·5% for BED and 0·1% for EDNOS-P. During early pregnancy, estimates were 0·2% (BN), 4·8% (BED) and 0·1% (EDNOS-P). Proportions of individuals remitting during pregnancy were 78% (EDNOS-P), 40% (BN purging), 39% (BED), 34% (BN any type) and 29% (BN non-purging type). Additional individuals with BN achieved partial remission. Incident BN and EDNOS-P during pregnancy were rare. For BED, the incidence rate was 1·1 per 1000 person-weeks, equating to 711 new cases of BED during pregnancy. Incident BED was associated with indices of lower socio-economic status.

Pregnancy appears to be a catalyst for remission of some eating disorders but also a vulnerability window for the new onset of broadly defined BED, especially in economically disadvantaged individuals. Vigilance by health-care professionals for continuation and emergence of eating disorders in pregnancy is warranted.