Breast cancer is the leading cause of cancer death of women worldwide. It has been well-established that carrying a pregnancy to term decreases the risk of breast cancer. However, chiefly for political reasons, the link between abortion and breast cancer is highly disputed in North America, despite 57 studies that show a positive association between abortion and breast cancer, of which 23 are statistically significant.1 17 studies show no link, but many of them have been criticized for their methodology.
Research has revealed that the longer a woman waits to have her first full-term pregnancy, the higher her risk of breast cancer, as her immature, cancer-vulnerable breast tissue is exposed to carcinogens for a longer duration.2
Additionally, there is evidence that induced abortion before 32 weeks gestation independently increases breast cancer risk. Confirmed by several studies, this link is explained by breast physiology.3 After conception, the embryo releases a hormone that causes an increase in estrogen and progesterone, which in turn cause breast cells to multiply. These new breast cells remain immature and cancer-vulnerable until after 32 weeks gestation, when 85 per cent of them mature into non-vulnerable cells.4 If a woman obtains an induced abortion before 32 weeks gestation, she retains the multiplied cancer-vulnerable breast tissue, making her more susceptible to breast cancer.
Various epidemiological studies confirm the abortion-breast cancer link and meet the Bradford-Hill criteria for establishing causality. In fact, abortion has been documented as the greatest predictor of breast cancer in nine countries.5
The effect of abortion on breast cancer risk must be publicized so that women can be fully informed before consenting to abortion.