The care of a pregnant breast cancer patient is a challenging clinical situation that historically has placed the welfare of the mother in conflict with that of the fetus. For the woman in this situation, the emotions usually associated with pregnancy can be overshadowed by the emotions aroused by a diagnosis of breast cancer and its subsequent treatment. The majority of published information on the management of breast cancer during pregnancy has consisted of retrospective chart reviews, case reports, and anecdotes. There is a paucity of published data from the prospective study of women who are pregnant at the time of their breast cancer diagnosis. This review will endeavor to address the diagnosis, staging, and subsequent treatment of breast cancer during pregnancy. The limited information available for this group of women on the outcomes of labor, delivery, and neonatal health will also be reviewed. This review will not specifically address pregnancy that occurs after diagnosis and subsequent treatment for breast cancer. However, some data, particularly those of an epidemiologic nature, address breast cancer diagnosed during pregnancy or within the year following delivery.