Size at birth and preterm birth in women with lifetime eating disorders: a prospective population-based study

To investigate whether eating disorders are associated with lower size at birth, symmetric growth restriction, and preterm birth; and whether pregnancy smoking explains the association between anorexia nervosa and fetal growth.

Longitudinal population-based cohort study.

Denmark.

Women from the Danish National Birth Cohort (n = 83 826).

Women with anorexia nervosa (n = 1609), bulimia nervosa (n = 1693) and both (anorexia + bulimia nervosa, n = 634) were compared with unexposed women (n = 76 724) (women with exposure data and singletons n = 80 660) using crude and adjusted linear and logistic regression models.

Size at birth (birthweight, length, head and abdominal circumference and placental weight); gestational age; small- and large-for-gestational-age (SGA, LGA); ponderal index, abdominal/head circumference.

Lifetime anorexia nervosa and lifetime anorexia + bulimia nervosa were prospectively associated with restricted fetal growth and higher odds of SGA [respectively, OR = 1.6 [95% CI 1.3-1.8] and OR = 1.5 [95% CI 1.2-1.9)] compared with unexposed women. Active anorexia nervosa was associated with lower birthweight, length, head and abdominal circumference, ponderal index, higher odds of SGA [OR = 2.90 (95% 1.98-4.26)] and preterm birth [OR = 1.77 (95% CI 1.00-3.12)] compared with unexposed women. Pregnancy smoking only partly explained the association between anorexia nervosa and adverse fetal outcomes.

Maternal anorexia nervosa (both active and past) is associated with lower size at birth and symmetric growth restriction, with evidence of worse outcomes in women with active disorder. Women with anorexia nervosa should be advised about achieving full recovery before conceiving. Similarly, targeting smoking in pregnancy might improve fetal outcomes.

Anorexia nervosa predicts small size at birth, small-for-gestational-age and symmetric growth restriction.