Birth characteristics, sibling patterns, and acute leukemia risk in childhood: a population-based cohort study

Background: The occurrence of acute lymphoblastic leuke-mia (ALL) and acute myeloid leukemia (AML) during child-hood may be influenced by factors operating in fetal life. Furthermore, childhood ALL has been suggested to be linked to patterns of infection during infancy. Purpose: To explore these hypotheses and other associations, we studied the impact of sibling patterns (e.g., birth order) and birth characteristics (e.g., birth weight) on the risk of childhood ALL and AML. Methods: By linkage of records of popula-tion-based registries, a cohort of all children whose mothers were born in Denmark from April 1935 through March 1978 was established. Children who developed ALL or AML dur-ing the period from April 1968 through December 1992 were identified by linkage with the Danish Cancer Registry. Birth weights were obtained for children born during the perio