Maternal folate supplementation in pregnancy and protection against acute lymphoblastic leukaemia in childhood: a case-control study

Background Acute lymphoblastic leukaemia is the most common childhood cance r in more-developed countries but it has few recognised risk factors or pre ventive measures. We aimed to determine and assess the risk factors associa ted with this disease. Methods From 1984 to 1992, we investigated known and suspected risk factors for common acute lymphoblastic leukaemia diagnosed in a population-based c ase-control study of children aged 0-14 years in Western Australia. 83 chil dren in the study group came from the sole referral centre for paediatric c ancer in the state and 166 controls matched for age and sex were recruited through a postal survey of people randomly selected from the state electora l roll. We interviewed mothers of 83 study and 166 control children (82% an d 74%, respectively, of those eligible). Fathers completed a self-administe red questionnaire. Findings We recorded a protective association between iron or folate supple mentation in pregnancy and risk of common acute lymphoblastic leukaemia in the child (odds ratio 0.37 [95% CI 0.21-0.65]; p=0.001). For iron alone, th e odds ratio was 0.75 (0.37-1.51); only one mother took folate without iron . Further analyses of folate use with or without iron (0.40; 0.21-0.73) sho wed that the protective effect varies little by time of first use of supple ments or for how long they were taken. The association was not weakened by adjustment for potentially confounding variables. Interpretation Our results, though unexpected, suggest that folate suppleme ntation in pregnancy reduces the risk of common acute lymphoblastic leukaem ia in the child.