Robin Edelstein (Robin Edelstein) and her colleagues measured the levels of the four hormones (testosterone, cortisol, estradiol and progesterone) in samples of saliva taken from 29 expecting couples. The study involved men and women aged 18 to 45 years. Saliva was taken four times: on the 12th, 20th, 28th and 36th weeks of pregnancy.

Previously, scientists had already observed that production of male hormones changed after the birth of a child, but for the first time this phenomenon is discovered during pregnancy. Future mothers climbed the development of all four hormones, while men were falling testosterone levels (which are associated with aggression) and estradiol (it is believed that he is responsible for the affection and care). The production of cortisol (stress hormone) and progesterone remained at the same level.

"We do not know exactly what is behind hormonal changes in men. Perhaps this is a consequence of the psychological changes that they are experiencing, preparing to become fathers. It is also likely that the main reason is that changes in the nature of a romantic relationship before the baby is born. Finally, during pregnancy may vary and the body of the father (not mother)," said lead author of the article.