Health Facts: No, Abortion Doesn’t Cause Breast Cancer
Opponents of reproductive choice have spent years attempting to frighten women by touting a non-existent link between abortion and an increased risk of breast cancer. There is no evidence of such a link and the claim is not supported by research scientists or breast cancer activists. Nonetheless, anti-choice organizations continue their attempts to disseminate this myth through advertising campaigns and so-called ‘informed consent laws.’
The faulty arguments used to demonstrate the non-existent link between abortion and breast cancer are based on selected “case studies.” These studies have crucial methodological flaws that complicate the supposed abortion/cancer link.
Many of these flawed studies asked women to report their abortion history retrospectively, often many years after the abortion procedure. This sort of retrospective data gathering can lead to reporting bias (or “recall bias”) that can confuse the data. Further, women who have been diagnosed with breast cancer are more likely to report having had an abortion, because they are identifying their early risk factors and are likely to recall ones that have been cited in the press, such as abortion or oral contraceptive use.1
As a result of these methodological flaws in the case studies, the relationship between abortion and breast cancer seems greater than it actually is.
In contrast to case studies, more accurate information is obtained from “prospective cohort studies.” In these investigations, researchers start tracking study participants in the present time and follow them for many years to get information about a specific question: in this case, which women develop breast cancer later in life. The format of these studies means that participants are much less likely to suffer from recall and reporting biases.
None of the prospective cohort studies have found a significant association between breast cancer and having had an abortion. A table summarizing the results of the more recent rigorous cohort studies can be found here.
In early 2014, a meta-analysis from China that seemed to find a relationship between breast cancer and abortion received a lot of attention from anti-abortion activists.2 The study was filled with methodological flaws that severely limit its validity, however. Specifically, the analysis reviewed 36 previous Chinese studies, only 8 of which had well-designed methodologies. And, none of these 8 well-conducted studies showed a significant relationship between breast cancer and abortion. Many of the other poorly designed studies were not published in peer-reviewed journals, which is the scientific gold standard for reliable evidence. The study also included contradictory findings of whether abortion-related stigma played a role in women’s reporting of having had the procedure.
Since 2003, the National Cancer Institute (NCI) and the American College of Obstetricians and Gynecologists (ACOG) have consistently reviewed the evidence on abortion and cancer and assessed the research. These leading medical experts have consistently and unanimously agreed that the evidence is strong that having an abortion does not increase a woman’s risk of breast cancer.
As a result of the NCI and ACOG review of available evidence, the organizations declared that recent studies demonstrated no “causal relationship between induced abortion and a subsequent increase in breast cancer risk.” The organizations re-examined the evidence again and reaffirmed this statement in 2009 and 2013.3
Studies with robust methodological designs repeatedly find no indication that having an abortion increases a woman’s risk of breast cancer. For example:
- One of the strongest studies on abortion and breast cancer, a 1997 Danish study published in The New England Journal of Medicine, reported on the experience of over 300,000 women who had had abortions.4 It found that those women were no more likely to develop breast cancer than were the 1.2 million women with no history of abortion.
- A large prospective study reported on by Harvard researchers in 2007 included more than 100,000 women and found no connection to breast cancer for either spontaneous or induced abortions.5 Women were tracked between 1993 and 2003. Since they were asked about abortion at the start of the study, recall bias was unlikely to play a role in the findings.
- In 2008, the California Teachers Study reported on 100,000 women who had been followed since 1995.6 The participants were asked about past induced and spontaneous abortions at the start of the study in 1995. More than 3,300 participants developed breast cancer; there was no difference in cancer risk between women who had had an abortion and those who had not.
- The Collaborative Group on Hormonal Factors in Breast Cancer conducted a large and expansive meta-analysis of 53 studies in 16 countries that included 83,000 women in 2004; it concluded that “the totality of worldwide epidemiological evidence indicates that pregnancies ending as either spontaneous or induced abortions do not have adverse effects on women’s subsequent risk of developing breast cancer.”7
There is currently no scientifically-based reason for women to fear an increased risk of breast cancer if they choose not to continue a pregnancy.
Countering the Anti-Choice Scare Tactics
Anti-choice organizations have long used this supposed correlation between abortion and breast cancer to incite fear and promote their anti-abortion agenda. In January 1996, Christ's Bride Ministries, a pro-life organization, published misleading advertisements in the transit systems of several cities including Washington, D.C., Baltimore, Philadelphia, and Chicago. These ads stated that: "women who choose abortion suffer more and deadlier breast cancer."
The public health, reproductive rights, and breast cancer advocacy communities responded quickly. Dr. Philip Lee, Assistant Secretary of Health in the U.S. Department of Health and Human Services, wrote a letter stating that the ad is ‘unfortunately misleading, unduly alarming, and does not accurately reflect the weight of the scientific literature.’ The National Cancer Institute issued a fact sheet asserting that the statements in the ad "misrepresent the information in the scientific literature."8
And the National Breast Cancer Coalition, a grassroots advocacy organization, published a position paper stating that the current evidence of abortion's relationship to breast cancer is inconclusive, and pointing out that "the abortion rate has been fairly constant since 1978, while breast cancer incidence continues to rise."9
Other anti-choice activists have found additional ways to use this scare tactic on women. Many states have considered and/or passed legislation requiring clinicians to provide women seeking abortions with false information about the increased risk of breast cancer. As of June 2015, states with such legislation include Alaska, Kansas, Mississippi, Oklahoma, and Texas.10
Breast cancer and reproductive rights activists are working to prevent the passage of laws requiring women to hear medically inaccurate information and to ensure that women get sound medical advice when considering abortion care.
Watch for Anti-Choice Scare Tactics in Your Community
The National Women's Health Network is committed to ensuring that women have access to accurate, balanced information about abortion and breast cancer. Keep an eye out for scare tactics in your community, and let us know what you find. If you have a question you would like to ask NWHN, submit it on our weekly Q & A column, "Since You Asked." Stay informed, connect with us on Facebook and Twitter
1. Schulz K, Grimes D, "Case-control studies: research in reverse," Lancet 2002; 359(9304): 431–4.
2. Huang Y, Zhang X, Li W et. al., "A meta-analysis of the association between induced abortion and breast cancer risk among Chinese females," Cancer Causes Control 2014; 25(2): 227-36.
3. American College of Obstetricians and Gynecologists (ACOG), “Induced Abortion and Breast Cancer Risk. ACOG Committee Opinion No. 434,” Obstet Gynecol 2009; 113: 1417–8. Retrieved on June 23, 2015 from: http://www.acog.org/Resources_And_Publications/Committee_Opinions/Committee_on_Gynecologic_Practice/Induced_Abortion_and_Breast_Cancer_Risk.
4. Melbye M, Wohlfahrt J, Olsen JH, "Induced abortion and the risk of breast cancer,” N Engl J Med 1997; 336: 81-85.
5. Michels K, Fei Xue M, Colditz G et al., “Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study,” JAMA 2007; 167:814-820.
6. Henderson K, Sullivan-Halley J, Reynolds P et. al., "Incomplete pregnancy is not associated with breast cancer risk: the California teachers study," 2008; 77(6):391-6.
7. Beral V, Bull D, "Breast cancer and abortion: collaborative reanalysis of data from 53 epidemiological studies, including 83 000 women with breast cancer from 16 countries," Lancet 2004; 363 (9414): 1007-016. Retrieved on June 23, 2015 from: http://www.ncbi.nlm.nih.gov/pubmed/15051280.
8. National Cancer Institute Website, Abortion, Miscarriage, and Breast Cancer Risk, Bethesda MD: National Cancer Institute 2010. Retrieved on June 23, 2015 from: http://www.cancer.gov/types/breast/abortion-miscarriage-risk.
9. National Breast Cancer Coalition Website, Abortion and Breast Cancer Risk: Position Statement, Washington, DC: National Breast Cancer Coalition 2011. Retrieved on June 23, 2015 from: http://www.breastcancerdeadline2020.org/breast-cancer-information/breast-cancer-information-and-positions/abortion-and-breast-cancer.pdf.
10.Guttmacher Institute Website, State Policies in Brief: Counseling and Waiting Periods for Abortion, Washington, DC: Guttmacher Institute 2015. Retrieved on June 23, 2015 from: http://www.guttmacher.org/statecenter/spibs/spib_MWPA.pdf.