Fetal androgen exposure and pragmatic language ability of girls in middle childhood: implications for the extreme male-brain theory of autism.

Prenatal exposure to testosterone has been shown to affect fetal brain maturation as well as postnatal cognition and behavior in animal studies. Although there are well-established sex-differences in the use of social communication (or 'pragmatic language') in humans, there has been limited investigation of the association between fetal testosterone exposure and postnatal pragmatic language ability. In this prospective study, pragmatic language skills, assessed using a pragmatic language score (PLS), were measured in 78 girls aged 10 years and correlated with testosterone levels in umbilical cord blood. A measure of the biologically active, 'free' fraction of testosterone, the free androgen index (FAI), was positively correlated with the PLS (R=.3). Regression analyses showed that the FAI was a significant, positive predictor of pragmatic language difficulties in girls after controlling for maternal and infant-health variables (B=0.02, 95% confidence interval=0.01-0.04, p=0.02). This is the first prospective study to identify an association between early life testosterone exposure and pragmatic language difficulties in girls. These novel findings are discussed with reference to the 'extreme male-brain' theory of autism.