BREAST-CANCER RISK IN MOTHERS OF TWINS

The risk of breast cancer associated with delivering a twin birth was examined in a population-based nested case - control study of nearly 4 800 Swedish women with breast cancer and 47000 age-matched control sub jects. AII were aged less than 50 years and parous. After adjustment f or age at first birth and parity, a 29% reduction in breast cancer ris k was observed in mothers of twins relative to those who were not (odd s ratio = 0.71, 95% confidence interval 0.55-0.91). These results prov ide evidence that women who bear twins are at reduced risk of breast c ancer, one explanation for which may be their unusual levels of hormon al exposure.