Mother's Cancer Can Pass to Fetus (tinguish between the infant's and mother...),Health

Based on this finding, the researchers believe cancer cells from the mother crossed the placenta and succeeded in implanting themselves into the fetus, unrecognized by the developing immune system.

The finding isn't all that surprising, one expert said.

"People have believed that this has been the case for some time. This is really crossing the Ts dotting the Is and showing that that's really the case," said William H. Chambers, scientific program director at the American Cancer Society.

He stressed that this type of transmission remains a rare occurrence. "I don't think people are going to decide that there are a whole lot more of these cancers," he said. "It's pretty rare that someone is going to find out they have a disease like this during or after pregnancy."

Mizutani agreed, but said precautions can still be taken.

"Malignant tumors are estimated to develop in one case of 1,000 pregnancies," Mizutani said. "The frequency of developing leukemia is estimated to be 1 in 75,000 to 100,000 pregnancies. Thus, although it might be rare, babies born in pregnant women who develop cancer during pregnancy should be placed under careful observation."

More information

For more information on leukemia, visit the American Cancer Society.

SOURCES: Shuki Mizutani, M.D., Ph.D., department of pediatrics, Tokyo Medical and Dental University, Japan; William H. Chambers, Ph.D., scientific program director, American Cancer Society, Atlanta; Oct. 12, 2009, Proceedings of the National Academy of Sciences, online