Tuesday 17th June 2008 News Index

If you're an expectant mother who likes to stand up for yourself, expect to hear the words "it's a boy!

Feisty females are more likely to give birth to boys than girls, according to the latest scientific research.

High levels of testosterone in the womb, which is normally evident in more aggressive women, provide a much better environment for the sperm coded to produce boys, scientists claim.

But even if you are having a particularly pugnatious pregancy, if you really want a daughter don't Ebay the pink paraphernalia just yet, because so far this link has been proved only in tests on animals.

The scientists who carried out the research, however, expect the same outcome will be seen in humans.

And there may be other reasons for expecting a boy.

Testosterone levels go up in women who are stressed, so if you are feeling anxious you could also be in line for a son, according to the scientific research.

It is the type of sperm which decides whether a child is a boy or a girl - if the sperm which fertilises the egg contains an X chromosome, a girl will be born; but if it is a Y chromosome, a boy is the result.

However the environment within a woman's womb affects the likelihood of different types of sperm making it to the egg ahead of the competition.

This study appears to show (in cows) a higher than average amount of testosterone in the womb makes it easier for Y-bearing sperm than X sperm.

Testosterone levels in women are linked to the characteristics of maternal dominance and aggression. Do you look after the TV remote control in your family?

To prove the link, scientists in New Zealand performed the following procedure. They extracted the follicles from cow ovaries, which contain eggs. The follicles were tested for levels of testosterone, and after that the extracted eggs were fertilised in the laboratory.

They worked out the sexes of the resulting embryos and statistically compared that with testosterone levels in the follicles from which they came.

Dr Valerie Grant, of Auckland University, who is Team Leader said: "Results showed that follicular testosterone levels were significantly higher for subsequently male embryos."

She said the fact that testosterone levels rose in women after experiencing chronic stress could mean that they were more likely to have boys after a nerve-racking experience.

Scientists had previously thought sex selection was a matter of pure chance based simply on which sperm reached the egg first.

But this could not explain how some animals had managed to change the ratio of male and females born as they had evolved.

Even if you do get a girl after a high-testosterone pregnancy, you may expect some tomboy behaviour from your pre-school girl, according to Avon Longitudinal Study of Parents and Children, a long-term study of biological, environmental and social factors associated with pregnancy outcomes and child health. A total of 13,998 pregnant women, who represented 90 percent of all pregnancies occurring in the Avon, England, area during an 18-month period in the early 1990s, enrolled in the study. Data from 679 offspring of the 14,138 children born during the study were analyzed.

Another clue as to the gender of your baby is how much you eat. It seems women expecting a boy eat 10% more than women expecting a girl, on average.

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