Maternal reproductive history and birth characteristics in childhood acute lymphoblastic leukemia.

Using birth-registration data, a case-control study was done to investigate the possible associations of childhood acute lymphoblastic leukemia (ALL) with birth characteristics and maternal reproductive history. The data included cases born and diagnosed in Minnesota since 1969. Matched analyses were conducted using 337 cases and 1336 birth year-matched controls. There was a statistically significant increased odds of ALL for birth to older (greater than 35 years) mothers (odds ratio (OR) = 2.14, 95% confidence interval (CI) = 1.28, 3.58), older fathers (OR = 1.62, 95% CI = 1.14, 2.30), mothers with at least a high school education (OR = 1.61, 95% CI = 1.05, 2.48), and larger intervals (greater than 5 years) between the birth of the proband and the preceding sibling (OR = 1.86, 95% CI = 1.12, 3.09). The increased odds of ALL for birth by Caesarean section approached significance (OR = 1.42, P = 0.06). No overall association was found for: gender, race, paternal education, fetal-loss history, birth order, prenatal care history, pregnancy complications, inducement of labor, multiple birth, gestational age, or birth weight. Age at diagnosis was an important effect modifier of some analyses. For cases diagnosed before age 2 years, there was a 2.7-fold increased odds of ALL if the last pregnancy had resulted in a fetal loss (P = 0.03). For cases diagnosed before age 4 years, birth weight greater than 3800 g was associated with a significant 2.05-fold increased odds of ALL. These data strengthen the hypothesis that prenatal events may play a causative role in childhood ALL, particularly in those cases diagnosed at a younger age.