Dick Swaab, professor of neurobiology at Amsterdam University, suggests a hypothesis regarding the adverse effect of the stress of a pregnant woman to her child.
Sunday Times: Mum’s lifestyle can determine baby’s sexuality
The Telegraph: Smoking increases chances of child being gay in adulthood, controversial study claims
He claims that some kind of stresses such as smoking and drinking of a pregnant woman will influence the health status of the fetus. And he also insists that a child who received much stress in emblionic age is likely to be a homosexual in later age. It seems to cause a broad discussion.
To be honest, his hypothesis is no more the newest one. Some research suggested that prenatal stress affected upon the sexual orientation of the child. The mice exposed to alcohol at the emblionic age tend to show an abnormality in sexual behaviors.
Pubmed: a test of the maternal stress theory of human male homosexuality.
Pubmed: Prenatal stress and ethanol exposure produces inversion of sexual partner preference in mice.
The controversy is whether homosexuality is a disease or not. Indeed, there is some evidence to suggest that homosexual persons have a certain abnormality about some endocrine system. However, sexual habits are also strongly influenced by nurture and cultural background. People who have a specific sexual orientation do not want to be deemed as disordered. In the past, American Psychiatric Association (APA) avoided dealing with this issue directly. The editors of Diagnostic Statistical Manual of Mental Disorders IVth edition (DSM-IV) made a vote to determine whether homosexuality was categorized as a mental disorder. Now, gay is not a disease at least in APA.
Nowadays, medical research has been able to distinguish some kind of diseases from the specific characteristics of the individual. However, it can be not desirable for some persons. For another example, Down's syndrome is almost predictable in the early stage of pregnancy. But it remains complicated what we should do after noticing that.