Breast cancer and pregnancy

Cancer is the second leading cause of death in women of child-bearing age. Carcinoma of the breast, an estimated 135,000 new cases of which were diagnosed in the USA in 1988, is the most common cancer in American women. Malignant disease complicates 1 in 1,000 pregnancies, with breast cancer diagnosed in but 1 of 3,500. Conversely, only 1% to 3% of breast cancers are associated with pregnancy and the period of lactation (the latter defined as the period of 1 year postpartum). In his review of world medical literature from 1850 to 1950, White found in a total of 45,881 women with breast cancer, only 1,296 cases (2.8%) occurring in pregnancy. Indeed, the bulk of breast cancer is diagnosed in post-menopausal women. Of 31,594 cases reported to the Cancer Registry of Norway from 1955 to 1980, women aged 50 and older comprised 73%, whereas women under the age of 35, less than 2% of the total. Breast cancer becomes significant, however, among the subgroup of women of childbearing age. In the same series of 31,592 women, 10% of those less than 35 years of age were pregnant at the time of diagnosis and an additional 15% had given birth within the year prior to diagnosis.