Birth characteristics, maternal reproductive history, hormone use during pregnancy, and risk of childhood acute lymphocytic leukemia by immunophenotype (United States).

OBJECTIVE: To investigate the associations of birth characteristics and maternal reproductive factors with risk of childhood acute lymphoblastic leukemia (ALL) by immunophenotypic subtypes.

METHODS: Data collected from a case-control study including 1842 ALL cases (age < 15 years) and 1986 individually matched controls were analyzed. Exposure information was obtained through telephone interviews of parents.

RESULTS: Factors associated with risk of ALL from all subgroups combined included high birth weight (OR = 1.4, 95% CI = 1.1-1.8), high birth order (OR = 2.0, 95% CI = 1.3-3.0 for fourth-born child compared to first-born child). young maternal age (<20 compared to 25-29, OR = 1.4, 95% CI = 1.1-1.9), advanced paternal age (>39 compared to 25-29, OR = 1.4, 95% CI = 1.0-1.9), induced abortion prior to the index pregnancy (OR = 1.2, 95% CI = 1.0-1.4), and oral contraceptive use during the index pregnancy (OR = 1.5, 95% CI = 1.0-2.2) with children under the age of 2 (OR = 5.1, 95% CI = 1.0-24.7) being the predominantly affected group. Risk of early pre-B-cell ALL increased with advanced paternal age (OR = 1.7, 95% CI = 1.1-2.7) and high birth order (OR = 2.0, 95% CI = 1.1-3.6), while risk of pre-B-cell ALL increased with both younger (OR = 3.4, 95% CI = 1.4-8.4) and advanced maternal age (OR = 2.6, 95% CI = 1.1-5.9). T-cell ALL was associated with high birth weight (OR = 2.4, 95% CI = 1.1-5.5) and history of induced abortion (OR = 2.4, 95% CI = 1.3-4.5).

CONCLUSION: This study suggests that the association of ALL with birth characteristics and maternal reproductive factors varies with the immunophenotype of the ALL. Future studies are needed to better understand the effect of maternal hormone in the development of subtype of childhood ALL.