title: Breast cancer risk in mothers of twins.
abstract: The risk of breast cancer associated with delivering a twin birth was examined in a population-based nested case-control study of nearly 4800 Swedish women with breast cancer and 47000 age-matched control subjects. All were aged less than 50 years and parous. After adjustment for age at first birth and parity, a 29% reduction in breast cancer risk was observed in mothers of twins relative to those who were not (odds ratio = 0.71, 95% confidence interval 0.55-0.91). These results provide evidence that women who bear twins are at reduced risk of breast cancer, one explanation for which may be their unusual levels of hormonal exposure.
authors.affiliation: ICRF General Practice Research Group, Radcliffe Infirmary, Oxford, UK.
authors.forename: M F
authors.initials: MF
authors.lastname: Murphy
authors.forename: M J
authors.initials: MJ
authors.lastname: Broeders
authors.forename: L M
authors.initials: LM
authors.lastname: Carpenter
authors.forename: J
authors.initials: J
authors.lastname: Gunnarskog
authors.forename: D A
authors.initials: DA
authors.lastname: Leon
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology*; D005260:Female; D006801:Humans; D016017:Odds Ratio; D010298:Parity; D013256:Steroids / Q000502:physiology*; D013548:Sweden; D014427:Twins
chemical_list: D013256:Steroids