Bisexuality is more common in men and women whose mothers received extra doses of the sex hormone progesterone during pregnancy. This is one of the evidence-backed assumptions of the scientific team of June Reinish, director of the Kinsey Institute in the US. Their research was published in the respected journal Archives of Sexual Behavior in April 2017. The study itself involved tracking the medical and sexual development of Danes whose mothers were treated with progesterone to prevent premature birth. According to the scientific team, progesterone is a highly underestimated factor influencing the development and variation of human sexuality, psycho-emotional development and sexual behavior. The hormone is widely used in the health care of expectant mothers, especially to prevent complications during pregnancy. Progesterone is produced in the bodies of both women and men. It has a number of regulatory functions, participates in the production of other sex hormones, affects various stress reactions of the body, ongoing inflammatory processes and plays an important role in the neurological development of the body. In modern medicine, progesterone and its synthetic versions are prescribed to facilitate the process of fertilization (at the cellular level) and increase the probability of conception, to prevent premature birth, and to increase the birth weight of the baby. NEWS_MORE_BOX Copenhagen University Hospital provided scientists with medical information on all Danes born at the hospital between 1959 and 1961. Among them, 17 women and 17 men were selected, whose mothers were given the progesterone drug lutocycline to prevent premature birth. The data of these people were compared and analyzed against the data of their peers who were born in the same hospital but had no contact with any progesterone preparations before their birth – they were the control group of the study. All study participants had very similar characteristics for their physical, medical, and socioeconomic factors. Both groups were studied in detail by doctors, psychologists and other medical professionals, including sexologists. According to the results, the children of women treated with progesterone were much less likely to self-identify as heterosexual – 20.6% or one in five people in this group had an atypical sexual orientation, as opposed to 3.2% in the control group. group. 24.2% of the participants were attracted to their own sex, and 17.6% were attracted to both sexes. Through their study, the scientists demonstrate the first link between progesterone intake during pregnancy and its potential effects on the child’s sexual behavior years later. Due to the complexity of hormonal dependencies and systems in the human body, it is difficult to determine whether the prenatal intake of progesterone preparations has other influences,but this requires further research with a larger number of participants, the scientists say. They want to set safe levels for progesterone medication to be taken by pregnant women, because the current maximum allowed doses are not supported by scientific research and it is not clear whether they have side effects on children, both in the womb and outside.