The air is thinner for the people of Tibet, who live more than 13,000 feet above sea level—more than 2 miles up and about as high as the top of Mauna Kea, the highest volcano in Hawaii. Some of those people have a genetic trait that allows their bodies to adapt better than others' by being able to absorb more oxygen in their blood; in women, this trait might give their children a better chance of surviving past infancy, according to a new study out of Case Western Reserve University.

What the researchers wanted to know: Do women who are better adapted to living at high altitudes have healthier babies?

What they did: The researchers and their assistants tramped through 14 villages over several years in the Himalaya Mountains and interviewed nearly all of the villagers who lived there. They talked to the women about their pregnancies and births, and tested the oxygen levels in everyone's blood. In all, they interviewed and tested nearly 3,000 people from 278 different families. Because the body's ability to absorb oxygen is influenced by many things and the researchers wanted to know specifically about women whose genes made them more efficient at it, the researchers inferred which women had the oxygen-absorbing gene using blood tests and the women's family histories.

What they found: Women whose genes made them better at absorbing oxygen had fewer children die in infancy than women who did not have that genetic structure. The genetically advantaged women had only an 8 percent chance of losing a child before his or her 15th birthday, while the risk increased to 43 percent for women who had low oxygen saturation levels. The researchers aren't sure if the mothers with the gene make (biologically) better parents or if their kids are more likely to have the gene as well, which helps them live longer.

What it means to you: Well, unless you're a Tibetan woman, this study doesn't really apply to your life. But it could show doctors how inherited characteristics can influence whether a child lives or dies.

Caveats: The researchers don't know the location of the specific gene that they were studying—or even if there is such a gene. They're pretty sure it exists, but they could only make an estimate as to who has it.

Find out more: Tibet is run by China now, but find out what the Government-in-Exile has to say about it at www.tibet.net

If you'd like to visit Tibet, the Lonely Planet website has advice for you.

For most moms, the biggest effect of high altitude will be altitude sickness. Find out about it and how to avoid it at familydoctor.org.

Read the article: Beall, C.M. et al. "Higher Offspring Survival Among Tibetan Women With High Oxygen Saturation Genotypes Residing at 4,000 M." Proceedings of the National Academy of Sciences. Sept. 28, 2004, Vol. 101, No. 39, pp. 14300–14304.

Abstract online: www.pnas.org