Birth weight appears associated with leukemia

By Michelle Rizzo

NEW YORK (Reuters Health) - There may be an association between high birth weight and an increased risk of overall leukemia and acute lymphoblastic leukemia (ALL). The increased risk of acute myeloid leukemia (AML) appears to be associated with the high and low extremes of birth weight.

"There is a growing body of evidence indicating that childhood leukemia is initiated in utero," the two study authors reported in the International Journal of Cancer.

Dr. Robert W. Caughey of the Harvard School of Public Health and Dr. Karin B. Michels of Brigham and Women's Hospital, Boston, conducted an analysis of 32 studies to examine the association between birth weight, childhood leukemia, plus ALL and AML, two common leukemia subtypes. Included in the analysis were 16,501 cases of all types of leukemia, 10,974 cases of ALL, and 1832 cases of AML.

Compared with normal birth weight, high birth weight was associated with a 35 percent overall increased risk of leukemia, a 23 percent increased risk of ALL and a 40 percent increased risk of AML.

For every 1000 gram increase in birth weight, the odds ratio for overall leukemia increased by 1.18.

While low birth weight was not associated with overall leukemia or ALL, there was an association between low birth weight and a 49 percent increased risk of AML.

"Our study supports the notion that childhood leukemia is likely to be initiated in utero," Michels said in an email interview with Reuters Health. "Birth weight is a marker for events during pregnancy that may have affected the risk for leukemia in the offspring."

"It will be important to investigate which factors may operate in utero that affect leukemia risk," Michels said. For example, leukemia risk may be affected by epigenetic factors, modifications to genes other than changes in the DNA sequence itself. Epigenetic modifications may include the addition of molecules, like methyl groups, to the DNA backbone and other factors that may indirectly influence the expression of the genome.

SOURCE: International Journal of Cancer, June 1, 2009.