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This is Morning Edition from NPR News. Good morning. I'm Renee Montagne. A couple of stories today in "Your Health." In a few minutes we'll hear how children with mild autism learn to improve their social skills. Now, they'll look at the debate on whether mothers can influence the gender of their babies. A British study found that women who ate lots of breakfast cereals, salt, and potassium were more likely to give birth to baby boys. As NPR's Allison Aubrey reports, there are still plenty of skeptics.

ALLISON AUBREY: If you remember high school biology, you may recall that it's the father who determines gender, right? If the man contributes a sperm bearing an X chromosome, the embryo becomes female. A Y sperm produces a male baby. And as far as statistician Stanley Young is concerned, that's the end of the story.

Dr. STANLEY YOUNG (Assistant Director of Bioinformatics, National Institute of Statistical Sciences): The female has relatively little, in fact nothing to do with the gender of the child.

AUBREY: Young is a bioinformatic's expert at the National Institute of Statistical Sciences. He says last spring when a prestigious British journal published a paper titled "You are What your Mother Eats," it prompted overnight buzz and thousands of Google hits. The paper concluded that what women eat in the months before they become pregnant does influence gender. But Stanley Young wasn't convinced.

Dr. YOUNG: The biological reasoning did not seem reasonable to me, and I looked at the statistics, but that didn't look reasonable either.

AUBREY: A British researcher at the University of Exeter named Fiona Mathews is the author of the paper. She says she understands Young's skepticism, but she says a growing body of research into evolutionary biology has scientists asking new questions. They're trying to understand what happens to embryos in utero, after sex is determined.

Not all embryos make it to birth. So perhaps the mother's environment, diet, or overall health does promote the survival of one gender over the other. With this thinking in mind, Mathews and her colleagues surveyed about 700 British mothers about their pre-pregnancy diets, asking about intake of lots of foods. She says it turned out that women who ate the most calorie-dense diets were more likely to deliver boys, but just slightly.

Dr. FIONA MATHEWS (Biologist, University of Exeter, England): If you went from being a woman in the lowest third of energy intake to upping your calories so that you're now in the top third of energy intake, you're switching your probability of having a boy from being about 45 percent to about 56 percent.

AUBREY: So, still close to 50-50 odds. Statistician Stan Young says he won't be convinced unless these findings can be replicated. And he says women shouldn't be led to believe that they can manipulate the odds of having a boy. Allison Aubrey, NPR News.

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