Risk of breast cancer in prematurely born women

The authors identified 273 girls born between 1925 and 1934. All of them were born before 35 weeks' gestation, weighing less than 2,000g. The breast cancer risk in women born before 31 weeks' gestation was 6.7 times that of the general population. Women born at 31 to 32 weeks' gestation had a 2- to 4-fold increase in risk. Women born after the 34th week who weighed less than 2,000 g at birth appeared to have a lower risk of breast cancer, in aggeement with other studies. These results confirm that there is a probable relationship between the perinatal hormonal environment and the risk of breast cancer.