SEARCH international case-control study of childhood brain tumours: role of index pregnancy and birth, and mother's reproductive history.

A series of co-ordinated population-based case-control studies of childhood brain tumours (CBT) was undertaken under the auspices of the Surveillance of Environmental Aspects Related to Cancer in Humans (SEARCH) programme of the International Agency for Research on Cancer (IARC) to evaluate, inter alia, the risk in relation to characteristics of the index pregnancy and birth, and maternal reproductive history. Subjects comprised 1218 cases aged 0-19 years and 2223 controls. Risk estimates were calculated by unconditional logistic regression, adjusted for age, sex, centre and mother's years of schooling, for all types of CBT combined as well as for four groups defined by histopathology (astrologlial tumours, primitive neuroectodermal tumours of the brain, 'other glial' tumours and 'other histological types') and for five age groups (0-1, 0-4, 5-9, 10-14, 15-19 years). Use of anaesthetic 'gas' was associated with an increased risk of CBT (OR = 1.5, 95% CI [1.1, 2.0]), apparent in children aged 0-4 years (OR = 2.4, 95% CI [1.4, 4.1]) and for astroglial tumours (OR = 1.6, 95% CI [1.1, 2.2]) with non-significantly increased relative risks for each of the other histological groups. However, not all centre-specific relative risks were elevated. No other aspect of the index pregnancy, delivery and early neonatal period or of the mother's previous reproductive history was associated with risk for CBT.