Health & Science
Can A Pregnant Woman's Diet Affect Baby's Sex?by Allison Aubrey
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A
controversial study suggests that a pregnant woman's diet, and perhaps
her environment and overall health, can influence the baby's sex. iStockphoto.com
Morning Edition, January 15, 2009 ·
Evolutionary biologists don't know much about how mothers might
influence the gender of their babies, but they've got lots of ideas. And
increasingly, they've got studies. A recent paper titled "You are what
your mother eats" found that women who ate lots of breakfast cereal,
salt and potassium were more likely to give birth to baby boys. The
study, published in
Proceedings of the Royal Society B, was based on surveys with 740 pregnant women who were unaware of the sex of their babies.
Skeptics Weigh InWhen
statistician Stanley Young, who works for the National Institute of
Statistical Sciences in Research Triangle Park, N.C., heard the buzz
over this paper, he was curious. And he was skeptical. Hadn't
scientists answered the question about how a baby's sex is determined
long ago? The high-school biology explanation is fairly
straightforward. The male determines the sex of offspring: If the man
contributes a sperm bearing an X chromosome, then the embryo becomes
female. A Y chromosome produces a male baby. It's a matter of chance.And
as far as Young is concerned, that's the end of the story. "The female
has nothing to do with the gender of the child," he says.After reading the paper, Young wrote to the editors at the
Proceedings of the Royal Society B and asked to see the data from the study."The
biological reasoning didn't seem reasonable to me. And I looked at the
statistics and it was complicated, but it didn't look reasonable
either," says Young.
Study Suggests Other Factors Could Influence SexThe
author of the study, Fiona Mathews, says she understands Young's
skepticism. "It's part of the scientific process," she notes. Yet she
stands behind her statistical methods and her findings."The
women who ate more (calories), including women who were more likely to
eat cereal in the morning, were more likely to bear boys than girls,"
says Mathews. "And it's highly unlikely that this occurred by chance."Mathews
explains that a growing body of research into evolutionary biology has
scientists asking new questions. They're trying to understand what
happens to embryos in utero. Not all fertilized eggs make it to birth,
so perhaps the mother's environment, diet or overall health does
promote the survival of one gender over the other. Despite the
higher incidence of baby boys among women who had more potassium and
sodium, Mathews says these are just correlations. It doesn't prove a
cause-and-effect. "The exciting thing is to try to work out
which factors are the crucial ones and how they're working to influence
the gender of the infant," she says.Much more research is needed
to untangle these questions. But Mathews says it's important for women
to realize they can't use the results as a formula for making baby
boys. In her study, women who consumed the most calories had a
56 percent chance of having a boy. Those who ate the fewest calories
had a 45 percent chance of giving birth to a boy.Either way, it's close to 50-50 odds.
Critics Call For Replication Of ResultsYoung's criticisms of the study have been published in the Jan. 14 issue of
Proceedings of the Royal Society B. He argues that Mathews and her colleagues may be wrong. "It's
hard to believe that woman can increase the likelihood of having a baby
boy by eating more bananas, cereal or salt," Young says.After
examining the data sets from the original study, which included
questions about 132 food items, he says it's likely that the
statistical significance with some of the foods including cereal and
salt were simply due to chance. "It's essential that multiple testing
be taken into account with transparent methods," Young says.Duly noted, say researchers in the field. "There
are lots of people interested in these questions," says Ian Rickard, an
evolutionary biologist at the University of Sheffield. "There's a lot
of compelling hypothesis and data, but we still don't have the full
picture."
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- Feb. 27, 2006
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- June 21, 2005
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- Dec. 14, 2004
Scott Huler: Boy Or Girl? I Don't Want To Know
Source: http://www.npr.org/templates/story/story.php?storyId=99346281