SMOKING and drug use during pregnancy can raise the chance of having a child who turns out to be gay, a leading neuroscientist claims.

Dr Dick Swabb, professor of neurobiology at Amsterdam University, argues the development of the brain during pregnancy and early childhood is directly linked to the kind of people we become in adulthood, according to Britain’s Sunday Times.

Dr Swabb’s new book, We Are Our Brains, cites multiple academic studies showing how an expectant mother’s lifestyle could possibly affect her baby.

One compared women whose mothers were given synthetic oestrogen during pregnancy between 1939 and 1960 in order to reduce the risk of miscarriage. The drug worked as it was intended, but it also turned out to increase the likelihood of bisexuality and lesbianism in the daughters of the women who took it.

"Pre-birth exposure to both nicotine and amphetamines increases the chance of lesbian daughters," Dr Swabb says.

"Pregnant women suffering from stress are also more likely to have homosexual children of both genders because their raised level of the stress hormone cortisol affects the production of foetal sex hormones."

Dr Swabb also links a mother's alcohol intake to possible lower IQ in her child.

"In women who drink a lot, cells that were meant to migrate across the foetal brain can end up leaving the brain altogether," he said.

"Even in women who drink just a glass of wine a day we see effects [such as] lower IQ and hyperactivity. There is no safe level."