Treating a woman with progesterone during pregnancy appears to be linked to the child's sexuality in later life. In a small-scale study, researchers found the children of these mothers were less likely to describe themselves as heterosexual by their mid-20s, compared to those whose mothers had not been treated with the sex hormone.
Progesterone is produced by both men and women. In the latter, it is involved in the menstrual cycle and helps foetus development – specifically neural development and the production of sex and steroid hormones. It also helps maintain pregnancies. For this reason, when women are at risk of miscarriage they are often treated with progesterone.
In a study published in the Springer journal Archives of Sexual Behaviour, a team led by June Reinisch from the Kinsey Institute in Indiana, followed 34 Danish people whose mothers were treated with progesterone during pregnancy.