Sexual dimorphism for cerebral asymmetry is already present at birth as a result of genetic programming, but the pattern of cerebral asymmetry changes after birth, suggesting that asymmetry may depend on shared environment as well as genetic factors. In neonates, cerebral asymmetry was more pronounced in girls than in boys in the prefrontal and occipital regions (Gilmore et al. 2007; Tanaka et al. 2012), while little consistency exists in sex-related and hemispheric differences in regional cortical volumes (Good et al. 2001; Raz et al. 2004). However, the left-greater than-right asymmetry in fetuses and neonates (Hering-Hanit et al. 2001; Gilmore et al. 2007; Ratnarajah et al. 2013) is opposite to that observed in older children (Caviness et al. 1996; Giedd et al. 1996; Reiss et al. 1996; Matsuzawa et al. 2001) and in adults (Nopoulos et al. 2000; Toga and Thompson 2003; Raz et al. 2004).
