Sara and Douglas Christensen believe their youngest daughter Lillie's autism is likely genetic because they have a nephew who also has autism. They'd like to know for sure, but that would require the kind of study that has never before been conducted.

Now Lillie — with her bright eyes, blond pigtails and beguiling indifference to the news conference that was going on around her Friday at Primary Children's Medical Center — is the human face of just such a study, although she will not be a participant.

She, her mom, Sara, and stuffed bear "Daisy Daffodil Buttercup Christensen" helped kick off the beginning to Salt Lake County's participation in The National Children's Study. The University of Utah and Salt Lake County were recently named among six "vanguard" or pilot centers for the study, set to begin recruiting within two years.

Before it's done, the study will have followed 100,000 pregnant women and the resulting infants from before birth (and in some cases before conception since women who might become pregnant are being recruited) until the child's at least 21. It will be conducted in 125 communities selected to represent America's demographics.

The study will examine genetics, environment and how the two interact to shape health and well-being, said Gov. Jon M. Huntsman Jr.

"It's the most ambitious, comprehensive study of children ever conceived," said Alan Fleischman, chairman of the study's federal advisory committee.

Researchers will be looking at psychological, social, biological and environmental factors that impact a child's well-being, he said. Of special interest are what happens during pregnancy, birth defects, asthma, obesity, diabetes and autism, among others.

That means researchers will be looking at air and dust in children's schools and homes, what they eat, how they are cared for, neighborhood safety, health care and much more, he said.

The researchers will also be storing a lot of biologic samples, said Dr. Cheryl M. Coffin, a professor of pathology at the U., who is spearheading local plans for collection and storage of blood, DNA, nail samples, hair, urine and possibly placenta tissue. It's a gargantuan undertaking. In just the Salt Lake County part of the study, a total of 85,000 blood samples will be collected in the first five years.

And while they're thinking in practical terms, like using liquid nitrogen to preserve some fluid samples and how new technology might keep DNA fresh at room temperature, they're also being creative. They are trying to imagine all the ways the samples might be needed in the future, when, perhaps, it can be paired with technology not yet even conceived.

Recruitment plans are being made now, in anticipation of the study actually beginning in 2007, said Sarah Keim, deputy director of the program office for the study, within the National Institutes of Health. It may follow census tracts or school boundaries or some other logical, statistically sound basis that ensures an end result that adds up to a picture of Salt Lake County's demography, from ethnicity to income.