Birth weight, leukaemia linked

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

"There is a growing body of evidence indicating that childhood leukaemia 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 leukaemia, plus ALL and AML, two common leukaemia subtypes. Included in the analysis were 16,501 cases of all types of leukaemia, 10,974 cases of ALL, and 1832 cases of AML.

Risk increase by 35%
Compared with normal birth weight, high birth weight was associated with a 35% overall increased risk of leukaemia, a 23% increased risk of ALL and a 40% increased risk of AML.

For every 1,000gr increase in birth weight, the odds ratio for overall leukaemia increased by 1.18.

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

Leukaemia initiated in utero
"Our study supports the notion that childhood leukaemia 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 leukaemia in the offspring."

"It will be important to investigate which factors may operate in utero that affect leukaemia risk," Michels said. For example, leukaemia 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. - (Michelle Rizzo/Reuters Health, June 2009)

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

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