Mum’s lifestyle can determine baby’s sexuality

This article originally appeared in the Sunday Times, January 19 2014.

A new study claims the choices made by pregnant women affect children’s brains and can increase their chances of being gay

By Jonathan Leake and Ben Lazarus

THE lifestyle adopted by a mother during pregnancy can radically change her  child, affecting everything from IQ to sexuality, claims a leading  neuroscientist.

In a new book Dick Swaab, professor of neurobiology at Amsterdam University,  suggests that factors ranging from taking synthetic hormones to leading a  stressful life can raise the chance of having a child who turns out to be  gay.

Similarly smoking, drinking and taking drugs designed to combat depression  during pregnancy can lower a child’s IQ, while living in an area with high  levels of traffic pollution can raise the risk of autism.

Swaab’s claims follow a survey of the latest academic studies about links  between the lifestyles of pregnant women and the development of their  babies. Each provides evidence of the sensitivity of the brain to outside  influences.

“If you know about brain development then it seems constantly amazing that it  usually goes so well,” said Swaab, the author of We Are Our Brains. “The  development of brains is so subtle that it can be changed very easily by the  unnatural things we take into our bodies.”

The brain begins to emerge in foetuses at the age of two weeks. A few cells on  the surface of the developing embryo quickly divide and grow to produce more  than 500bn cells that are then subjected to ruthless selection, leaving only  20% surviving into adulthood.

Those that survive are chosen for their ability to migrate to the correct  place in the brain and form connections with their neighbours — up to  100,000 in each cell.

“This is such a delicate process that anything that introduces toxins to our  bodies can disrupt it,” said Swaab.

“The effects can vary but the principle is the same. Once those changes have  been made then they are locked into place and that child has been changed  for ever.”

One demonstration of such changes came from studies of women whose mothers  were given synthetic oestrogen during pregnancy between 1939 and 1960 in  order to reduce the risk of miscarriage. While the drug did meet that aim,  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,” said Swaab.

“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.”

Some traits are dictated by nature, including the discovery that the more  older brothers a boy has, the greater the chance that he will be gay. This  may be due to a mother’s immune system developing stronger responses to the  male hormones produced by boy babies with each pregnancy.

Perhaps illustrating the point, Thomas Hitzlsperger, the former Aston Villa,  West Ham and German international footballer who announced that he was gay  earlier this month, has five older brothers and one sister.

Swaab emphasises that a mother’s lifestyle during pregnancy is just one of  many influences on the foetal brain, with genetics playing perhaps the most  important role of all.

His key point, however, is that the development of the brain during pregnancy  and early childhood is directly linked to the kind of people we become in  adulthood. In an era when medical imaging is exposing the links between  brain structure, personality and mental health, such a suggestion seems  obvious.

In the past it has proved highly controversial because it ran counter to the  view, popular among feminists in the 1970s and 1980s, that the differences  between men and women were entirely due to “social conditioning”, meaning  cultural and social influences.

Swaab was one of the first researchers to question this view and to show there  were structural differences between people’s brains that link to factors  such as sexuality and IQ.

“In boys, testosterone from the gonads changes brain structure, making some  areas larger and others smaller than in women,” he said.

“The idea that pregnant women could influence the brains of their developing  babies followed naturally from those findings.”

Swaab says alcohol has a particularly pronounced effect. “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.”

We Are Our Brains will be published by Allen Lane on January 30 at £20 or  £16 including free P&P from Sunday Times Books


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