CHICAGO (July 19, 2010)--For the first time, a large study suggests a higher rate of childhood cancer among test-tube babies, but Swedish researchers say the reason probably has nothing to do with the method.

More likely, it's related to the genetics of the parents who used in vitro fertilization because of infertility.

The study's authors and other experts say there could be another reason.

Test-tube infants often are born prematurely and have breathing problems at birth.

Both have also been linked with increased cancer risks.

But even with an elevated risk, far less than 1 percent of these children develop cancer.

The findings were published online Monday in Pediatrics.

Whether similar results would be found among U.S. children is uncertain.