Mammographic appearance of the breasts during pregnancy and lactation: false assumptions

It is believed that pregnant and lactating women have dense breasts, thereby limiting the usefulness of mammography. To our knowledge, no reports have been published on this topic for nearly 4 decades. The purpose of our study was to determine whether this assumption is accurate given current state-of-the-art mammography.

Mammograms of 18 women (six pregnant, seven lactating, and five who recently discontinued lactation) were examined and compared with their baseline (before pregnancy or lactation) mammograms and with mammograms of 18 age-matched control subjects. Studies were scored for breast density according to the Breast Imaging Reporting and Data System and evaluated for change in density and size.

Three of the six pregnant women had unchanged breast density compared with baseline studies and had scattered fibroglandular or heterogeneously dense tissue. Of the three without baseline studies, one had extremely dense, one had heterogeneously dense, and one had scattered fibroglandular tissue. All seven lactating women had either heterogeneously dense or extremely dense tissue. The breast tissue in four was unchanged in density and increased in two; no baseline study was available for the remaining patient. Seven studies in five women who had discontinued lactation 1 week to 5 months prior to mammography showed no change in density compared with baseline.

Pregnant and lactating women do not always have dense breasts, and mammography can be performed without substantial concern for the limitations of breast density. Mammography can be as useful in these women as it is in other women with breast signs and symptoms.