Explicit and implicit caregiving interests in expectant fathers: Do endogenous and exogenous oxytocin and vasopressin matter?

Caregiving interest in men (N=46) during the third trimester of their partner's pregnancy was examined. The study included both explicit and implicit measures of caregiving interest, assessments of basal urinary concentrations of oxytocin and vasopressin, and exogenous (intranasal) application of these hormones. Compared to control men (N=20), fathers-to-be reported more interest in direct care for children.

Maternal serum steroid levels are unrelated to fetal sex: a study in twin pregnancies.

Increased prenatal exposure to testosterone (T) in females of an opposite-sex (OS) twin pair may have an effect on the development of sex-typical cognitive and behavioral patterns. The prenatal exposure to T due to hormone transfer in OS twin females may occur in two ways, one directly via the feto-fetal transfer route within the uterus, the other indirectly through maternal-fetal transfer and based in the maternal-fetal compartment. Although some studies in singletons indeed found that women pregnant with a male fetus have higher T levels during gestation than women pregnant with a female fetus, many other studies could not find any relation between the sex of the fetus and maternal serum steroid levels.

Prenatal sex hormone effects on child and adult sex-typed behavior: methods and findings.

There is now good evidence that human sex-typed behavior is influenced by sex hormones that are present during prenatal development, confirming studies in other mammalian species. Most of the evidence comes from clinical populations, in which prenatal hormone exposure is atypical for a person's sex, but there is increasing evidence from the normal population for the importance of prenatal hormones. In this paper, we briefly review the evidence, focusing attention on the methods used to study behavioral effects of prenatal hormones.

Is there an effect of prenatal testosterone on aggression and other behavioral traits? A study comparing same-sex and opposite-sex twin girls.

Men and women differ in temperament and personality traits, such as aggression and sensation seeking. The sex hormone testosterone could play a role in the origin of these differences, but it remains unclear how and when testosterone could have these effects. One way to investigate the prenatal exposure effect of testosterone is to compare opposite-sex (OS) and same-sex (SS) female twins.

Prenatal exposure to testosterone and functional cerebral lateralization: a study in same-sex and opposite-sex twin girls.

In animals it has been shown that exposure to sex hormones is influenced by intrauterine position. Thus fetuses located between two male fetuses are exposed to higher levels of testosterone (T) than fetuses situated between two female fetuses or one female and one male fetus. In a group of opposite-sex (OS) twin girls and same-sex (SS) twin girls a potential effect of prenatal exposure to testosterone (T) on functional cerebral lateralization was investigated.