Abortion–breast cancer hypothesis
The abortion–breast cancer hypothesis posits that having an induced abortion can increase the risk of getting breast cancer. This hypothesis is at odds with mainstream scientific opinion and is rejected by major medical professional organizations; despite this, it continues to be widely propagated as pseudoscience, typically in service of an anti-abortion agenda.
In early pregnancy, hormone levels increase, leading to breast growth. The hypothesis proposes that if this process is altered by an abortion, then more immature cells could be left behind, and that these immature cells could increase the risk of breast cancer over time.
The abortion–breast cancer hypothesis has been the subject of extensive scientific inquiry, and the scientific community has concluded that abortion does not cause breast cancer; and that breast cancer should not be a concern for women who are having a miscarriage or considering having an abortion. This consensus is supported by major medical bodies, including the World Health Organization, the U.S. National Cancer Institute, the American Cancer Society, the American Congress of Obstetricians and Gynecologists, the Royal College of Obstetricians and Gynaecologists, the German Cancer Research Center, and the Canadian Cancer Society.
Some anti-abortion activists have continued to advance a discredited causal link between abortion and breast cancer. In the United States, they have advanced state legislation that in several states requires health care providers to present abortion as a cause of breast cancer when counseling women who are seeking abortion. This political intervention culminated when the George W. Bush administration altered the National Cancer Institute website to suggest that abortion might cause breast cancer. In response to public concern over this intervention, the NCI convened a 2003 workshop bringing together over 100 experts on the issue. This workshop concluded that while some studies reported a statistical correlation between breast cancer and abortion, the strongest scientific evidence from large prospective cohort studies demonstrates that abortion is not associated with an increase in breast cancer risk, and that the positive findings were likely due to response bias.
The ongoing promotion of a link between abortion and breast cancer is seen by others as part of the anti-abortion "woman-centered" strategy against abortion. Anti-abortion groups maintain they are providing information necessary for legally required informed consent, a concern shared by some politically conservative politicians. The abortion–breast cancer issue remains the subject of political controversy.