You are what Mom ate?

CHICAGO - What a woman eats before pregnancy influences her baby's gender, according to surprising new research released yesterday.

Having a hearty appetite, eating potassium-rich foods and not skipping breakfast all seemed to raise the odds of having a boy.

The British study is billed as the first in humans to show a link between a woman's diet and whether she has a boy or girl.

It is not proof. But it fits with evidence from test tube fertilization that male embryos thrive best with longer exposure to nutrient-rich lab cultures, said Tarun Jain, a fertility specialist at the University of Illinois at Chicago who was not involved with the study.

It might take more nutrients to build boys than girls, Jain said.

Lead author Fiona Mathews of the University of Exeter said the findings also fit with fertility research showing male embryos aren't likely to survive in lab culture with low sugar levels. Skipping meals can cause low blood sugar.

Jain said he was skeptical at first. But the study was well-done and merits followup, he said.

The idea may not be as far-fetched as it sounds. While men's sperm determine a baby's gender, it could be that certain nutrients or eating patterns make women's bodies more hospitable to sperm carrying the male chromosome, he said.

Other scientists said the results made sense in evolutionary biology: Boys tend to be bigger; creating them requires more nutrients.

The research was published in the Proceedings of the Royal Society B, a British medical journal.

For the study, 700 first-time pregnant women in the United Kingdom who didn't know their fetus' sex were asked about eating habits the year before pregnancy.

Among women with the highest calorie intake before pregnancy (but still within a normal, healthy range), 56 percent had boys, vs. 45 percent of those with the lowest calorie intake.

Women who ate at least one bowl of breakfast cereal daily were significantly more likely to have boys than those who ate no more than one bowlful per week. Cereal is a typical breakfast in Britain, and the researchers said they considered eating very little of it to be a possible sign of skipping breakfast.

The women who had boys ate an average of 300 more milligrams of potassium daily - often from bananas - than those who had girls. They also ate about 400 more calories a day overall, Mathews said.

Still, no one recommends pigging out if you really want a boy or starving yourself if you'd prefer a girl.

Neither is healthy, and other research suggests obese women have a harder time getting pregnant.

Plus, the habits studied were merely at opposite ends of normal.