The role of maternal environment on calibrating "Mini Puberty" in early infant development.

The postnatal period is a time of increased brain development and plasticity which have enduring influences on brain and behavior. Infants demonstrate a transient surge in testosterone (T) during development referred to as "mini puberty". The utility of studying mini puberty in psychobiology has only recently emerged. Life-history theory postulates that infants "use" the maternal environment-pre and postnatally-to calibrate growth and timing of sexual maturity. As such, variability in infant T levels is not arbitrary and can be predicted by theory. We examine the role of maternal pre- and postnatal cortisol. Using saliva samples (n = 193 dyads), we predicted that higher levels of maternal cortisol are associated with higher levels of infant T. We found only maternal postnatal cortisol had a relationship with infants' mini puberty. This relationship was in the predicted direction and remained after controlling for numerous variables. Discussion will include the potential role of mini puberty as an inflection point where systems related to growth, sexual maturation, and psychosexual behavior can be calibrated and coordinated.