Throughout the second and third trimesters, the human placenta (and the placenta in other anthropoid primates) produces substantial quantities of corticotropin-releasing hormone (placental CRH), most of which is secreted into the maternal bloodstream. During pregnancy, CRH concentrations rise over 1000-fold. The advantages that led selection to favour placental CRH production and secretion are not yet fully understood. Placental CRH stimulates the production of maternal adrenocorticotropin hormone (ACTH) and cortisol, leading to substantial increases in maternal serum cortisol levels during the third trimester. These effects are puzzling in light of widespread theory that cortisol has harmful effects on the fetus. The maternal hypothalamic-pituitary-adrenal (HPA) axis becomes less sensitive to cortisol during pregnancy, purportedly to protect the fetus from cortisol exposure. Researchers, then, have often looked for beneficial effects of placental CRH that involve receptors outside the HPA system, such as the uterine myometrium (e.g. the placental clock hypothesis). An alternative view is proposed here: the beneficial effect of placental CRH to the fetus lies in the fact that it does stimulate the production of cortisol, which, in turn, leads to greater concentrations of glucose in the maternal bloodstream available for fetal consumption. In this view, maternal HPA insensitivity to placental CRH likely reflects counter-adaptation, as the optimal rate of cortisol production for the fetus exceeds that for the mother. Evidence pertaining to this proposal is reviewed.

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This study examines steroid production in fathers watching their children compete, extending previous research of vicarious success or failure on men's hormone levels. Salivary testosterone and cortisol levels were measured in 18 fathers watching their children play in a soccer tournament. Participants completed a survey about the game and provided demographic information. Fathers with higher pregame testosterone levels were more likely to report that referees were biased against their children's teams, and pre- to postgame testosterone elevation was predicted by watching sons compete rather than daughters as well as perceptions of unfair officiating. Pregame cortisol was not associated with pregame testosterone or with perceived officiating bias, but cortisol did fluctuate synergistically with testosterone during spectator competition. Although fathers showed no consistent testosterone change in response to winning or losing, pregame testosterone may mediate steroid hormone reactivity to other aspects of their children's competition.