Very high birth weight of offspring is associated with an increased risk of leukemia in their mothers: results of a population-based cohort study.

Although the association between birth weight and childhood leukemia is well described, the relation between a child's birth weight and parental risk of leukemia is unknown. We linked data from the Jerusalem Perinatal Study to the Israel Cancer Registry to ascertain the incidence of leukemia in mothers and fathers in relation to their offspring's birth weight. Birth weight >or=4500 g in any of the offspring was associated with a >3-fold risk of leukemia in mothers, but not fathers. Potential mechanisms include shared exposures of high birth weight infants and their mothers, possibly to radiation or growth factors, or genetic pathways leading to both high birth weight and leukemia.