An examination of the biodevelopment of gender expression in children ages 6-to 12-years

Previous clinical research on children who experience gender dysphoria has demonstrated links between marked childhood gender variant behaviour and several variables thought to provide a window on biological processes affecting brain sexual differentiation during the pre-/perinatal period. These variables include handedness, birth order, and birth weight. The present study investigated, via parent-report, whether these factors were associated with inter-individual variation in childhood gender expression in a large community sample (n = 2377, 51.4% boys). Consistent with previous studies, elevated gender variance was associated with non-right-handedness in boys and girls, and later fraternal birth order in boys. In contrast to prior clinical studies, there were no associations between gender expression and birth order in girls, and no interactions of birth weight and birth order in predicting gender variance in boys. Thus, handedness in both genders and late fraternal birth order in boys appear to apply widely as predictors of inter-individual variation in childhood gender expression, whereas the other factors examined here may only predict more marked levels of gender variance as examined in previous clinical research of children who experience gender dysphoria.