Taken from the September/October 2016 issue of the Women's Health Activist Newsletter.
The faulty arguments used to promote 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 confuse data and analysis. 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 received media attention, like 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 at a certain time and follow them for many years to get information about a specific question: in this case, which women are likely to 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 rigorous cohort studies is available at: https://ww5.komen.org/BreastCancer/Table25Abortionandbreastcancerrisk.2
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.3 The study, however, was filled with methodological flaws that severely limit its validity. Specifically, the analysis reviewed 36 previous Chinese studies, only eight of which had well-designed methodologies. And, none of these eight 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 about 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 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 2013.4
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.5 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.6 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 1995.7 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.”8
The bottom line is: there is currently no scientifically-based evidence that abortion leads to an increased risk of breast cancer.
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. Back in 1996, the anti-choice group Christ's Bride Ministries published misleading ads 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 “misrepresent the information in the scientific literature.”9 And the National Breast Cancer Coalition published a position paper pointing out that “the abortion rate has been fairly constant since 1978, while breast cancer incidence continues to rise.”10
Despite the outcry from the public health community, anti-choice activists are using misinformation as a way to scare women out of having an abortion. Many states have considered and/or passed legislation forcing clinicians to provide women with false information about the effects of abortion, including the purported connection with breast cancer.
Currently, 17 states mandate that women seeking abortion care be given “counseling” that includes specific misinformation.11 Five states (Alaska, Kansas, Mississippi, Oklahoma, Texas) mandate that women seeking abortion care receive medically inaccurate information that abortion leads to breast cancer.12,13 North Dakota requires that its abortion counseling materials discuss “the possible increased risk of breast cancer.”14 (Twelve states mandate that women be given misinformation about the fetus’ ability to feel pain, and seven states mandate provision of medically inaccurate information on abortion’s long-term mental health effects.15,16
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. The NWHN is committed to ensuring that women have access to accurate, balanced information about the all reproductive services, including abortion. Keep an eye out for scare tactics in your community, and let us know what you find. Email us at firstname.lastname@example.org.
The continued availability of external resources is outside of the NWHN’s control. If the link you are looking for is broken, contact us at email@example.com to request more current citation information.
1. Schulz KF, Grimes DA, "Case-control studies: research in reverse," Lancet 2002; 359(9304): 431-434. doi:10.1016/S0140-6736 (02)07605-5.
2 .Susan G Komen Foundation, Abortion and Breast Cancer Risk,
3. 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. doi: 10.1007/s10552-013-0325-7. Epub 2013 Nov 24.
4. American College of Obstetricians and Gynecologists (ACOG), “Induced Abortion and Breast Cancer Risk. ACOG Committee Opinion No. 434.” Obstet Gynecol 2009; 113: 1417–8. Available online at: http://www.acog.org/Resources_And_Publications/Committee_Opinions/Committee_on_Gynecologic_Practice/Induced_Abortion_and_Breast_Cancer_Risk.
5. Melbye M, Wohlfahrt J, Olsen JH, "Induced abortion and the risk of breast cancer,” N Engl J Med 1997; 336: 81-85. doi: 10.1056/NEJM199701093360201..
6. Michels KB, Fei Xue MD, Colditz GA, et al., “Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study,” JAMA 2007; 167:814-820.
7. Henderson, KD, 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. doi: 10.1016/j.contraception.2008.02.004. Epub 2008 Apr 18.
8. 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. Available online at: http://www.ncbi.nlm.nih.gov/pubmed/15051280.
9. National Cancer Institute (NCI), Abortion, Miscarriage, and Breast Cancer Risk, Bethesda MD: NCI, January 12, 2010.
10. National Breast Cancer Coalition (NBCC), Abortion and Breast Cancer Risk: Position Statement, Washington, DC: NBCC, Updated June 2010.