Abortion does not increase the chance of being diagnosed with breast cancer. In 2003, the National Cancer Institute (NCI) convened a workshop with over 100 scientists, who evaluated the current strength of studies addressing the association between reproductive events and the risk of breast cancer. The participants concluded that induced abortion is not associated with an increase in breast cancer risk. Studies published since 2003 continue to support this conclusion. Further, major health organizations around the world agree with this conclusion, including the World Health Organization, 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.
Many studies of the relationship between prior induced abortion and breast cancer risk have been found to be methodologically flawed, especially studies that depended on small samples, or “case control” studies that use control groups of women without breast cancer – who tend to under-report their abortions compared to case groups of cancer-stricken women looking for possible causes. This skews the results of case control studies, making it appear that women with breast cancer had more abortions and creating an apparent association.
More rigorous recent studies (the best ones are called “prospective” or “cohort” studies) demonstrate no causal relationship between induced abortion and a subsequent increase in breast cancer risk, because they don’t depend on women self-reporting their abortions.
Nevertheless, anti-choice groups continue to attempt to dissuade women from choosing abortion by promoting the discredited link and exploiting their fear of breast cancer.
Sources:
American College of Obstetrics & Gynecology, ACOG Committee Opinion: Induced Abortion and Breast Cancer Risk (2009)
Planned Parenthood Federation of America, Myths About Abortion and Breast Cancer (2003)
Dr. David A. Grimes, Abortion and Breast Cancer: How Abortion Foes Got It Wrong (2015)
Rewire, How Deeply Flawed Studies on Abortion and Breast Cancer Become Anti-choice Fodder, by Joyce Arthur (2014)
The Guardian, A scientist weighs up the five main anti-abortion arguments, by David Robert Grimes (2015)