Maternal Eating Disorders Influence Sex Ratio at Birth

Abstract

Previous studies have shown that low maternal weight, a diet low in certain fats, higher stress levels, and lower androgen levels are associated with fewer male births, but no association has been reported between maternal eating disorders and sex ratio at birth (defined as the proportion of male live births). This prospective, population-based, cohort study was conducted as part of the Norwegian Mother and Child Cohort Study. A total of 38,340 pregnant women at a median of 18.6 weeks gestation completed a questionnaire on eating behavior that reflected DSM IV criteria for four eating disorders: anorexia nervosa, binge eating disorder, bulimia nervosa, and eating disorders not otherwise specified-purging type (EDNOS-P). Estimates of the sex ratio at birth were determined for women with singleton live births and eating disorder diagnoses. Poisson regression analyses were used to estimate unadjusted and adjusted proportions and ratios for factors known to affect the sex ratio at birth, including mother's age, marital status, prepregnancy body mass index (BMI), maternal education, lifetime smoking status, income, gestational age, and parity. Compared to a reference group, unadjusted analyses showed that proportions of male live births were 10% lower for mothers with anorexia nervosa and 8% lower for mothers with bulimia nervosa. A higher proportion of male births was found among mothers with maternal binge eating disorder (4%) and EDNOS-P (28%). Adjustment for covariates did not affect the results. These data suggest an association between the sex of offspring and maternal eating disorders. The specific eating disorder subtype appears to influence the direction of the effect.