Mammograms were obtained from 942 normal women aged over 30 years, and were classified by Wolfe's criteria. In women with an enhanced risk of breast cancer associated with a late age at first child or nulliparity, there was a significant increase in the proportion of P2 and DY mammographic patterns which are thought to be a radiological index of risk. There was a decrease in the proportion of P2 and DY grades in women using steroidal contraceptives. However, the association between radiological and epidemiological determinants of risk did not hold for age at menarche.

Mammograms were obtained from 942 normal volunteer women aged over 35 years, and were classified by Wolfe's criteria. There was no relationship between height and mammographic pattern. An increase in weight, whether corrected for height or not, was associated with an increase in the proportion of N grades and a concomitant decrease in DY grade mammograms. This effect reached formal significance in pre-menopausal women but was highly significant in post-menopausal women. For women who were either above or below their ideal weight there was a significant positive correlation between parity and the proportion of N and P1 mammograms. The slopes of the linear regression for these two groups were the same, although the elevation of the above-ideal weight group was significantly greater. This implies that for any given parity, there are about 16% more N or P1 grades in the above-ideal compared with the below-ideal weight group.