Abortions increased from 69,499 in 1984 to 106,255 in 1994. The number of new breast cancer cases reported for the first time nationally in 1984 was 10,321 and rose to 17,000 in 1994. It was estimated that in 1996 there would be 18,600 new cases of breast cancer and that 14 Canadian women would lose their life to breast cancer each day. In the last 20 years, the share of abortions has increased for women who had been pregnant less than 13 weeks, for women in their 30's and for those women who had at least one prior induced abortion. Scientists agree that the earlier in a woman's life that her breast cells reach maturity due to a full term pregnancy, the more protected she is against the possibility of developing breast cancer.
Breast cancer is believed to originate in undifferentiated or primitive cells.
Prior to conception a woman's breasts consist mostly of connective tissue surrounding a branching network of ducts with relatively few milk producing cells. At conception there is a surge of oestradiol or estrogen production and the milk buds begin to develop a duct-like form preparatory to lactation at birth. During the first trimester the breast cells are in a 'transitional' or undifferentiated stage and are vulnerable to cancer until the cells begin to differentiate or 'specialize' in the second and third trimester under the direction of other hormones produced in the later stages of pregnancy. At full term pregnancy, the stabilized cells result in mature breast tissue which will never again be as vulnerable to breast cancer. Estrogen exposure is known to promote tumour growth.