From Our 2009 Archives

Is Mom's Diet a Key to Her Baby's Sex?

Researchers Question Findings of Study That Linked Breakfast Cereal to Delivery of Boys

By Kathleen Doheny
WebMD Health News

Reviewed By Louise Chang, MD

Jan. 14, 2009 -- A woman who eats breakfast cereal every day around the time of conception is not more likely to deliver a boy than a girl, contrary to the findings of a study published last year, say U.S. researchers who reanalyzed the original data.

But the authors of the original study, conducted in the U.K., stand by their conclusions; they say the U.S. researchers are overlooking their "big picture" finding -- that the status of a mother's diet prior to conception may influence whether she delivers a boy or a girl.

In the original study, British researchers who looked at the diets of 740 newly pregnant women had concluded that 59% of those who ate breakfast cereal daily around the time of conception gave birth to boys, while 43% of those who never or rarely ate breakfast cereal before conception had boys.

They asked the women to keep food logs before conception, during early pregnancy, and later on in pregnancy. They only found a link between the sex of the child and a mother's nutritional status around the time of conception.

They also found that women with higher calorie intakes before conception were more likely to have boys. While 56% of the women who took in the most calories had boys, only 45% of those who took in the least number of calories prior to conception had boys. The study was published in 2008 in the Proceedings of the Royal Society B.

New Look at Study's Findings

"The study has no evidence that what you eat has any effect on gender," says S. Stanley Young, PhD, lead author of the reanalysis and assistant director for bioinformatics at the National Institute of Statistical Sciences, a nonprofit research organization in Research Triangle Park, N.C.

His report is published online today in the Proceedings of the Royal Society B.

Young says he was alerted to the study and decided to take a look, reanalyze the data, and see if he reached the same conclusions. He says the British group continued to investigate a potential link between food intake and the baby's sex even when previous answers about dietary habits didn't support such an association -- a statistical misstep.

Trying to influence the sex of an unborn baby has been "of enormous interest forever," says Young. "If something as simple as eating cereal would have made any difference, we probably would have figured it out by now."

Looking at the 'Big Picture'

Meanwhile, the study authors stand by their findings, noting in a reply to the criticism, also published online in the journal, that the U.S. scientists are overlooking their primary finding about the "big picture" dietary patterns of pregnant women.

"Mothers' intakes of a range of nutrients are linked with the sex of the infant," Fiona Mathews, DPhil, lecturer in mammalian biology at the University of Exeter, England, the study's lead author, tells WebMD in an email.

Mathews also says that the U.S. team "applied a nonstandard statistical method to the data from my work."

She points to two other studies, both published in 2008, that support the hypothesis that the maternal environment around conception may favor the survival of "girl" sperm (with X chromosome) or "boy" sperm (Y chromosome).

"One [study] looked at maternal weight change between pregnancies and found that women who gained more weight were more likely to have sons," she says. The other found that women with eating disorders that resulted in reduced calorie intake were less likely to have boys.

Second Opinion

Two infertility specialists who reviewed the study and reanalysis for WebMD side with the U.S. researchers, although one says the "maternal environment" may influence gender.

The association between cereal and gender is "a random event," says David Adamson, MD, a fertility specialist in Palo Alto and San Jose, Calif., and immediate past president of the American Society for Reproductive Medicine.

Even if it is not a chance association, he says, it does not prove cause and effect.

Any link between cereal eating and the sex of the baby is a "random chance event," agrees Steven Ory, MD, a past president of the American Society for Reproductive Medicine and a fertility specialist in Margate, Fla.

"What we've learned about sex selection in the recent past is that it's ultimately determined by the father," he says, although he adds that there may be some factors in the mother's reproductive tract that may make it more likely for "girl" or "boy" sperm to meet the egg.

The best advice for mothers-to-be? Ory and others recommend a healthy, well-balanced diet before conception and during pregnancy. "I don't think there is any realistic hope that their cereal is going to influence the sex of their baby."

SOURCES: Stanley Young, PhD, assistant director of bioinformatics, National Institute of Statistical Sciences, Research Triangle Park, N.C. Young, S. Proceedings of the Royal Society B, online, Jan. 14, 2009. Fiona Mathews, DPhil, lecturer in mammalian biology, University of Exeter, England. Mathews, F. Proceedings of the Royal Society B, online, Jan. 14, 2009. Mathews, F. Proceedings of the Royal Society B, July 22, 2008; vol 275: pp 1661-68. Bulik, C. Acta Obstetricia et Gynecologica Scandinavica, Issue 9, 2008; vol 87: pp 979-81. Villamor, E. Fertility & Sterility, May 2008; vol 89: pp1240-1244. David Adamson, MD, fertility specialist, Palo Alto and San Jose, Calif.; immediate past president, American Society for Reproductive Medicine. Steven Ory, MD, past president, American Society for Reproductive Medicine; fertility specialist, Margate, Fla.

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