Mammographic density changes during the menstrual cycle.

The ability to detect small tumors is impaired in dense mammograms. It has been suggested that the sensitivity of mammograms could be lower in mammograms obtained during the luteal phase of the menstrual cycle. We examined the change in mammographic density from the follicular to the luteal phase of the menstrual cycle in 11 women. Although the average increase in densities was quite small (1.2%; P = 0.08), six women had clinically significant increases (1.4-7.8%), suggesting that premenopausal women should undergo mammographic examinations in the follicular part of the menstrual cycle.