From womb to words: the sex-specific interplay of fetal sex hormones and maternal mood on infant language development.

INTRODUCTION

Language development is influenced by biological and environmental factors, including infant hormonal status and maternal mental health. Previous research on the role of infant sex hormones in language development focused on estradiol and testosterone, yet first evidence indicates that dehydroepiandrosterone (DHEA), the dominant fetal steroid hormone, may be a more sensitive biomarker for language development by shaping the organization of the developing brain. Concerning infants' language-learning environment, maternal well-being is a key factor, with maternal depressed mood postpartum, even at subclinical levels, negatively affecting language development, as depressed mothers engage less with their children and use less infant-directed speech. The present study examined the interplay of fetal DHEA levels and maternal mood at eight weeks postpartum on receptive language abilities at 12 months in boys and girls.

METHODS

Fetal DHEA levels were extracted from hair samples collected two weeks after birth (n = 58; 28 girls), allowing fetal hormone milieu quantification in the third trimester. Maternal mood in the subclinical depression range was assessed using the Edinburgh Postnatal Depression Scale. Children's receptive language abilities were assessed using the German version of the Bayley Scales of Infant and Toddler Development.

RESULTS

Stepwise multiple linear regression analysis revealed fetal DHEA to predict language development in boys, with the effect depending on maternal mood. Only when mothers experienced better mood postpartum were higher DHEA levels related to lower language ability. By contrast, in girls, only maternal mood significantly contributed to language ability, with better mood relating to higher language outcome.

DISCUSSION: Our findings suggest that the effect of infant sex hormones on language development follows sex-specific patterns and appears to be modulated by the learning environment. Moreover, our results emphasize the importance of mental support during the early stages of language development.