National Abortion Federation- Abortion and Breast Cancer

Abortion and Breast Cancer
Printable version of this fact sheet (PDF file, 63K)

Scientific Research
Breast cancer is a very important health concern for women. For all women, the risk of breast cancer increases with age. According to the National Cancer Institute, this risk rises from about 1 in 252 for a woman in her thirties, to about 1 in 27 for a woman in her sixties, to a lifetime risk of about 1 in 8.1 Discovering the causes of this disease is a high priority for research scientists around the world.

Since 1981 several dozen studies investigating whether abortion increases a woman's risk of developing breast cancer have been published. The results of the studies often seem contradictory, which can be confusing and frightening for women who are considering having an abortion. Many of the older studies alleging a link between breast cancer and abortion were flawed, since some included only a small number of women, and most used a scientifically unreliable method dependent upon self-reported abortion data.2 Newer studies that rely on more accurate methods have consistently shown no association between abortion and an increased breast cancer risk.3

What the Experts Say
In February 2003, the National Cancer Institute, a branch of the National Institutes of Health, convened a workshop that evaluated studies on abortion and breast cancer and assessed whether an association between abortion and breast cancer exists. Over 100 of the world's leading experts on pregnancy and breast cancer, including epidemiologists, clinicians and breast cancer advocates participated.4

These experts concluded that studies have clearly established that "induced abortion is not associated with an increase in breast cancer risk."4 This conclusion was reviewed and unanimously approved by the NCI's top scientific advisors and counselors.4

Types of Studies
In order to understand which studies give us the most accurate information, it is helpful to know more about how the studies are done. There are two basic ways to conduct research on this topic; one looks backward in time at the abortion experiences of women who have breast cancer, and the other looks forward in time at the development of breast cancer among women who have had abortions.

In case-control studies, scientists compare women who have breast cancer with similar women who do not. Both groups are asked whether they have had abortions in the past.
In cohort studies, scientists compare women who have had abortions and similar women who have not. Both groups are examined again as years pass to determine whether they develop breast cancer.

Case-Control Studies and Recall Bias
Of the two, case-control studies have a higher likelihood of inaccurate results because healthy women and women with cancer report information about their medical history differently. When healthy women are asked very personal questions about their sexual lives, especially about a topic as sensitive as abortion, there is a strong tendency not to report truthfully on abortions they have had. On the other hand, women being treated for breast cancer are strongly motivated to give their doctors very accurate information, and they are less likely to forget to report an abortion they have had. Comparing the two groups of women, those with breast cancer will appear to be more likely to have had abortions, even if this is not actually the case. Scientists call this difference in how women report their medical history "recall bias."

A 1996 case-control study among Dutch women5 demonstrated how recall bias works. Scientists found that in areas of the country where abortion is socially accepted, women with breast cancer and women without breast cancer reported equal numbers of past abortions. But in regions where attitudes about abortion are less tolerant, healthy women reported fewer past abortions than women with breast cancer. Because it is not reasonable to assume that abortion leads to breast cancer in one place but not in another, the researchers concluded that attitudes about abortion led some of the healthy women to under-report their abortions if they lived in places where abortion was not socially accepted. Other case-control studies have found similarly conflicting results, with some suggesting that abortion and breast cancer may be linked, and others finding no connection at all.

Cohort Studies
Cohort studies are not affected by recall bias, because scientists monitor the women directly from the time of their abortions until the time of any breast cancer diagnosis, and they do not need to rely on potentially faulty memories of past events. Scientists consider the results of cohort studies to be much more accurate than case-control studies. Cohort studies, however, take many years to complete and they are very expensive, so fewer of them are done. Of all cohort studies which have been published to date, none have shown a link between abortion and breast cancer.

The research problems discussed above can be overcome when accurate and complete life-long medical records are kept. In some European countries, where the government maintains a complete health registry on each citizen, studies using these unbiased records can be very informative. In fact, the most convincing cohort study of abortion and breast cancer involved over 1.5 million women in Denmark.6 Using data from national registries, scientists found that abortion had no overall effect on the risk of breast cancer.

Some Additional Facts
A single study reporting a link between two events does not, by itself, prove that the first event caused the second. Both events might be caused by some unknown third factor.

Some anti-choice organizations have worked hard to stir up fears that abortion causes breast cancer even though there is a strong consensus in the scientific community that no such link exists. Anti-choice groups promote these scientifically unwarranted conclusions as if they were established facts in order to frighten women and discourage them from having an abortion. Anti-choice activists are opposed to legal abortion under almost any circumstances, regardless of its safety. Their real goal in this controversy is preventing women from exercising their legal right to choose abortion, not protecting women's health.

If you are considering abortion, your health care provider can give you the most up to date information on new research on abortion and the risk of future breast cancer.

References

National Cancer Institute, Lifetime Probability of Breast Cancer in American Women.

National Cancer Institute, Cancer Facts, March 2003. See also section of this fact sheet entitled "Types of Studies."

National Cancer Institute, Cancer Facts, March 2003.

See National Cancer Institute, Summary Report: Early Reproductive Events and Breast Cancer Workshop

Rookus, M.A. & van Leeuwen, D.A. "Induced Abortion and Risk for Breast Cancer: Reporting (Recall) Bias in a Dutch Case-Control Study." Journal of the National Cancer Institute, 1996, 88(23): 1759-1764.

Melbye, M. et al. "Induced Abortion and the Risk of Breast Cancer." The New England Journal of Medicine, 1997, 336(2): 81-85.

Planned Parenthood Factsheets and Reports

Use the links below to read fact sheets and reports related to Abortion Access.

06.01.06
Abortion After the First Trimester

01.18.07
The Emotional Effects of Induced Abortion

07.03.00
Laws Requiring Parental Consent or Notification for Minors' Abortions

12.29.06
Medical and Social Health Benefits Since Abortion Was Made Legal in the U.S.

12.13.06
The Difference Between Emergency Contraception And Medication Abortion

12.13.06
How Abortion Is Provided

03.01.02
The Facts Speak Louder than the Silent Scream

01.02.04
Nine Reasons Why Abortions Are Legal

01.02.04
Five Ways to Prevent Abortion

05.01.06
Mifepristone: Expanding Women's Options for Early Abortion

01.14.03
George W. Bush's War on Women: A Pernicious Web

08.09.06
Anti-Choice Claims About Abortion and Breast Cancer

01.03.05
Profiles of 15 Leading Anti-Choice Organizations

08.02.04
Teenagers, Abortion, and Government Intrusion Laws

01.02.01
Donating Fetal Tissue for Treatment and Research

06.01.00
Medical Training for Abortion and Contraceptive Services

Abortion and Breast Cancer: An Evidence Based Perspective

Position Paper 70 Abortion Rights Coalition of Canada June 2005

Abortion and Breast Cancer: An Evidence-Based Perspective

All women have the right to be presented with pregnancy options in a non-judgemental, unbiased manner. Bias, misinformation, and coercion are a violation of the fundamental rights of all women. The anti-choice movement commonly uses misinformation to scare women out of having abortions. Of the many false statements presented as fact, one of the most common is the purported link between breast cancer and therepeutic abortion. However after evaluating current, reliable evidence on the subject, ARCC, in agreement with the vast majority of all reputable medical associations, believes that there is no link between therepeutic abortion and the development of breast cancer.

What do Current Scientific Studies and Medical Associations Say About The Link Between Abortion and Breast Cancer?

Determining whether there is a link between abortion and breast cancer(ABC) has been the subject of extensive scientific research. The anti-choice movement is able to manipulate some data because literature prior to the 1990s was largely inconsistent- many studies have serious
methodological flaws(small sample size, insufficient controls for variability, researcher bias). More contemporary studies, which corrected the above mentioned methodological flaws, show that there is no demonstrable link between therepeutic abortions and breast cancer; there is neither an increase nor decrease in breast cancer among women who have had a therepeutic abortion(for specific references, please consult the endnotes).

Perhaps the most significant evidence refuting the ABC link comes from the National Cancer Institute (NCI) in the United States. In 2002, the NCI posted a report on its website dispelling myths about ABC. When this report was criticised by anti-choice members of Congress, the NCI held a conference, 'Early Reproductive Events and Breast Cancer' in 2003 in Bethesda, MD. This conference brought together 100 cancer experts and epidemiologists to examine the data and provide a clear statement of fact. Their conclusion was that it is well established that induced abortion[a.k.a therepeutic abortion] is not associated with an increased risk of breast cancer.

Several other organisations have also produced position statements with regards to the so-called ABC link. The Society of Obstetricians and Gynaecologists of Canada and the Society of Gynecologic Oncologists of Canada released a joint committee opinion statement in May 2005, which maintains there is no link between either spontaneous abortion(miscarriage) or therepeutic abortion and the increased risk of breast cancer. The American College of Obstetricians and Gynaecologists Committee on Gynecologic Practice released an opinion statement in August 2003, with the finding that early studies demonstrating an ABC link were inconclusive, and that more recent studies argue against a link between abortion and breast cancer. The Canadian Cancer Society, which monitors risk factors as they pertain to cancers, agree with the NCI findings that there is no association between abortion and breast cancer.

What About Advertising That States That There is a Link Between Abortion and Breast Cancer?

Data that claims to support a link between abortion and breast cancer is highly biased. First, those who advertise an ABC link are connected to organisations with the primary goal of restricting abortion, not reducing rates of breast cancer. Second, the few studies that suggest an ABC link are now considered to be out-of-date, and were not of a particularly high standard to begin with. These studies took sample sizes that were too small (i.e. small sample sizes are not representative of the whole population), and relied on patient recall rather than following people over a period of time.

Conclusion

Unfortunately, it is all too easy to pas off false information as fact. Anyone can make a website that looks professional, and anyone can write a press release. When faced with any piece of information, especially something with far-reaching consequences, it is important to be vigilant in questionng the source of such statements.
There are a few simple ways to do this:

1. Look for references. The best references come from good, peer reviewed journals. If the information is important enough, and is sound, it will get into a good journal.
2. Look at the age of the resources. Information changes over time as we learn more and more about a topic.
3. Check the affiliations of the organisations and researchers doing the studies.
4. Beware of personal opinions. They are just that- opinions not fact.

Sources

Brewster DH et al. 'Risk of Breast Cancer after miscarriage or induced abortion: a Scottish record linkage case-control study' J Epidemiol Community Health 2005; 59; 283-287

Canadian Cancer Society. 'Abortion and Breast Cancer' Accessed Online October 1, 2005 at: http://cancer.ca/ccs/internet/standard/0,2704,3172_369425_langId-en,00.html

Collaborative Group on Hormonal Factors in Breast Cancer. '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; 1007-16.

Committee on Gynecologic Practice, American College of Obstetricians and Gynaecologists. 'ACOG committee opinion. Induced abortion and breast cancer risk. Number 285, August 2003.' Int J Gynaecol Obstet. 2003 Nov;83(2);233-5.

Erlandsson G, Montgomery SM, Chattingius S, Elkborn A. 'Aboritons and breast cancer' Int J Cancer 2003; 103(5);676-9.

Lash TL, Fink AK. 'Null association between pregnancy termination and breast cancer in a registry-based study of parous women'. Int J Cancer 2004; 110; 443-448.

Mahue-Giangreco M, Ursin G, Sullivan-Halley J, Bernstein L. 'Induced Abortion, Miscarriage, and Breast Cancer Risk of Young Women' Cancer Epidemiology, Biomarkers and Prevention 2003; 12; 209-214.

National Cancer Institute. 'Summary Report: Early Reproductive Events and Breast Cancer Workshop'. Accessed online October 1, 2005 at: http://www.cancer.gov/cancerinfo/ere-workshop-report-report

Paoletti X, Clavel-Chapelon F. 'Induced and Spontaneous abortion and breast cancer risk: results from the E3N cohort study' Int J Cancer 2003: 106(2); 270-6.

Society of Obstetricians and Gynaecologists of Canada/ Society of Gynegologic Oncologists of Canada. 'Breast Cancer and Abortion', JOGC 2005; 27(5); 491.

Ye Z, et al. 'Breast cancer in relation to induced abortions in a cohort of Chinese women.' Br J Cancer 2002; 87; 977-981.

The So-Called 'Post-Abortion Syndrome'

A small number of studies, based primarily on anecdotal evidence, claim to document the incidence of 'post-abortion syndrome' (PAS). Symptoms of this supposed condition include feelings of grief, depression, anger, guilt, and discomfort with small children and pregnant women. Alleged behavioural manifestations include frequent crying, flashbacks, sexual inhibition, and alcohol abuse (Speckhard, 1985).

Although only a minority of women report severe negative effects post-abortion, the idea that abortion has severe negative effects continues to be widespread by abortion opponents (Boyle, 1997; Russo and Denious, 2001). The fact is that anti-abortion groups have invented this condition to further their cause. The American Psychiatric Association does not recognise 'post-abortion syndrome' (1994), and all of the studies that purport to prove PAS contain methodological flaws that render their conclusions nongeneralisable beyond their subjects.

The most damning flaw common to all of these studies is that only women who already self identified as having problems with abortion were recruited for them.

For example:

• In her doctoral dissertation, 'The Psycho-Social Aspects of Stress Following Abortion', Anne Catherine Speckhard chronicled how 'abortion functions as a stressor' (Speckhard 1985). However she drew her conclusions from a subject pool of 30 women who 'had high stress abortion experiences' (Speckhard, 1985). As a result, in unpublished correspondence, her doctoral adviser clarified that Speckhard's 'findings apply only to the 30 women who volunteered to participate in her study and to absolutely no one else' (Boss, 1986). In fact there is little evidence to support the notion that abortion will lead to severe psychological sequelae among the general population of women. The American Psychological Association assembled an expert panel to review the evidence of psychological risks of abortion. This panel concluded 'the weight of the evidence from scientific studies indicates that legal abortion of an unwanted pregnancy in the first trimester does not pose a psychological hazard for most women (Beckman, 1998).
• In his survey of women who had abortions, David Reardon found that 94% of his respondents experienced negative psychological effects (Reardon, 1987). However he used a biased subject pool, drawing only from members of an anti-choice group called Women Exploited by Abortion (WEBA).
• To demonstrate that adolescents suffer greater psychological consequences after abortion than adults, Wanda Franz and David Reardon examine data from ' a survey of organisations[such as WEBA] serving as support groups for women who have had negative reactions to abortion' (Franz and Reardon, 1992). They conclude by making generalisations about the effects of abortion on all adolescents, even though they derive their data from a non-representative, highly biased subject pool. In fact, a recent study of young women found that there is no evidence that abortion poses a threat to adolescents' psychological well being (Pope, 2001).
• In an unpublished but widely circulated paper, Terry Selby limits her discussion of 'post-abortion trauma' to 'a population of women who have presented themselves in a general mental health practice with a variety of presenting psychological and psycho-social issues' (Selby, 1984).

Overall Conclusions by Health Experts.

• In 1989, A panel of experts assembled by the American Psychological Association concluded unanimously that legal abortion 'does not create psychological hazards for most women undergoing the procedure'. The panel noted that, since approximately 21 percent of all U.S. women have had an abortion, if severe emotional reactions were common there would be an epidemic (Adler, 1989). Since 1989, there has been no significant change in this point of view.

Cited references

Adler, Nancy E (1989). University of California at San Francisco, Statement on Behalf of the American Psychological Association Before the Human Resources and Intergovernmental Relations Subcommittee of the Committee on Governmental Operations, US House of Representatives: 130-40.

Boyle, Mary (1997). Re-thinking abortion: Psychology, Gender, Power and the Law. New York: Routledge

Franz, Wanda and David Reardon. (1992) 'Diffreential Impact of Abortion on Adolescents and Adults.' Adolescence, 27(105), 161-72.

Pope, Linda, et al. (2001) 'Postabortion Psychological Adjustment: Are minors at Increased Risk? Journal of Adolescent Health, 29(1), 2-11.

Russo, Nancy Felipe, and Jean E. Denious. (2001) Violence in the Lives of Women Having Abortions: Implications for Practice and Public Policy'. Professional Psychology; Research and Practice, 28(1), 23-31.

Selby, Terry L. (1984) Post Abortion Trauma. Unpublished paper.

Speckhard, Anne Catherine. (1985). The Psycho-Social Aspects of Stress Following Abortion: A Thesis. Doctoral dissertation, University of Minnesota.

RCOG- Abortion and Breast Cancer

Royal College of Obstetricians and Gynaecologists 11 August 2000

Abortion and Breast Cancer
In March 2000 the RCOG published an Evidence Based Guideline on "The Care of Women requesting Induced Abortion". Induced abortion is one of the most commonly performed gynaecological procedures in Great Britain. Around 180,000 terminations are performed annually in England and Wales and around 12,000 in Scotland. At least a third of British women will have had an abortion by the time they reach the age of 45. The Guideline Development Group view induced abortion as a healthcare need. The aim of the guideline was to ensure that all women considering induced abortion have access to a service of uniformly high quality. The guideline summary is available on the RCOG website (www.rcog.org.uk).

The guideline includes many aspects of abortion care including the provision of information for women about potential complications. One these recommendations reviews the evidence of the association between breast cancer risk and abortion. (shown below)

The RCOG wishes to reassure women who have had an abortion or who have breast cancer that the research evidence on this question to date is INCONCLUSIVE. The association found in some studies has not been found in others of equal quality. Indeed studies based on the linkage of national registers on induced abortion and breast cancer which are less open to bias than case-control studies which rely on recall of subjects have not shown any significant association.
Breast cancer risk: available evidence on an association between induced abortion and breast cancer is inconclusive. (Grade B)

Two carefully conducted meta-analyses examining the relationship between induced abortion and subsequent breast cancer have been published. The two reviews have reached different conclusions about the nature of any association. The validity of case-control studies of abortion and breast cancer have been seriously questioned because of the evidence that there is a significant difference between cases and controls in their willingness to reveal whether or not they have had an abortion. Studies based on the linkage of national registers on induced abortion and breast cancer are less open to bias than case-control studies relying on recall of subjects.

Two such studies have not shown any significant association.
A recent review from Grimes' group has highlighted the differences in validity of the various available studies. When only those studies least susceptible to bias are included, the evidence suggests that induced abortion does not increase a woman's risk of breast cancer in later life.

WHO- Induced Abortion Does Not Increase Breast Cancer Risk

World Health Organisation Factsheet 240- June 2000

Induced abortion does not increase breast cancer risk

Breast cancer
Cancer of the breast is common in developed countries where the lifetime risk ranges from 1 in 12 to 1 in 20 women. Among women living in developing countries the risk is lower but appears to be increasing. Risk factors for breast cancer include high socio-economic status, early menarche, late first birth, late menopause, and a family history of breast cancer.

Induced abortion
Currently, in countries where induced abortion is permitted by law, which have total fertility rates of about 2 or less and high prevalence rates of contraceptive use, the annual rate of induced abortion is 1 to 2 abortions per 100 women of reproductive age. In these countries on average, almost every second woman has an abortion during her life. In countries with similar fertility rates but much lower prevalence of contraceptive use, the annual rate of induced abortion is higher and can be estimated to be up to 10 or more per 100 women annually. In countries where abortion is permitted by the law, the large majority of abortions (typically > 90 %) take place before the end of the 12th week of pregnancy.

Risk of breast cancer following induced abortion
Most of the information on whether induced abortion modifies the risk of breast cancer among women comes from epidemiological studies, which are either case-control studies, or historical cohort studies. For information on abortion, all published case-control studies have relied on interviews of cases and controls with the inherent problem of recall bias. This bias occurs because women with breast cancer (cases) tend to truthfully report induced abortion while controls, who often are healthy women, have no "incentive" to provide information about personal and sensitive matters such as induced abortion. Such bias can produce elevated relative risk estimates in case-control studies. As a result, the outcome of such studies has been inconsistent, with some having indicated a small increase in risk, while others have not.

Historical cohort studies, on the other hand, are more methodologically sound. Two major studies have been carried out using this methodology, and neither found an increased risk of breast cancer associated with first trimester abortion.

Therefore, results from epidemiological studies are reassuring in that they show no consistent effect of first trimester induced abortion upon a woman’s risk of breast cancer later in life.

Further reading
Lindefors-Harris B-M et al. American Journal of Epidemiology 1991;134:1003-8.
Daling et al. Journal of the National Cancer Institute 1994;86:1584-92.
Brind et al. Journal of Epidemiology and Community Health 1996;50:481-96
Meirik et al. Journal of Epidemiology and Community Health 1998;52:209-11
Lindefors Harris B-M et al. British Medical Journal 1989;299:1430-2
Melbye M et al. New England Journal of Medicine 1997;336:81-5
Daling et al. American Journal of Epidemiology 1996;144:373-80
McCredie M et al. International Journal of Cancer 1998:76:182-88.
Bartholomew LL and Grimes DA. Obstetric and Gynaecological Survey 1998;53:708-14.
Blettner et al. Journal of Epidemiology and Community Health 1997;51:465

Anti-Choice Claims About Abortion and Breast Cancer

Studies have shown that abortion is not associated with breast cancer. Undaunted by the absence of compelling evidence, anti-choice extremists insist on making the connection anyway. Once more they are using misinformation as a weapon in their campaign against safe, legal abortion.

Anti-choice zealots in the United States have drwn highly questionable conclusions to develop 'public education' campaigns such as the advertisements sponsored by Christ's Bride Ministries that have appeared on public transportation vehicles in Philadelphia warning that 'women who choose abortion suffer more and deadlier breast cancer' (Slobozian, 1999). These misinformation campaigns have used many forms of media and advertising to mislead women about abortion, including television, billboards, bumper stickers and print ads (Simon,2002).

Anti-abortion foes are also lobbying for legislation in the US that would require telling women who are considering abortion that having one would place them at an incresed risk for breast cancer (Querido,1999).

Anti-Choice claims linking abortion and breast cancer fly in the face of of scientific evidence. The National Cancer Institute (NCI) in the United States, the American Cancer Society (ACS) and the American College of Obstetricians and Gynaecologists (ACOG) have alll refuted of such an association (ACS, 2003; ACOG, 2003; NCI, 2003).

Rigorous Studies Dismiss Association
In February 2003, NCI convened the Early Reproductive Events and Breast Cancer Workshop to 'provide an integrated scientific assessment of the association between reproductive events and the risk of breast cancer'. After reviewing the body of scientific literature, NCI concluded that 'Induced abortion is not associated with an increase in breast cancer risk' (NCI, 2003).

In August 2003, after conducting its own review of scientific literature, ACOG issued a committee opinion concluding that 'early studies of the relationship between prior induced abortion and breast cancer risk have been inconsistent and are difficult to interpret because of methodologic considerations. More rigorous recent studies argue against a causal relationship between induced abortion and a subsequent increase in breast cancer risk' (ACOG, 2003).

Three of the Strongest Studies Published to Date Show No Overall Relationship Between Induced Abortion and Breast Cancer
One of the most highly regarded studies on abortion and breast cancer was published in the New England Journal of Medicine in 1997. This study of 1.5 million found no overall connection between the two (Melbye et al., 1997). This study benefited from its size- 1.5 million women- and by linking data from the National Registry of Induced Abortions and the Danish Cancer Registry, thereby avoiding one of the pitfalls observed in some case control studies- that women with breast cancer were more likely to recall having had an induced abortion than women without breast cancer, particularly because aboriton had been illegal (Brody, 1997; Westhoff, 1997). An accompanying editorial on the results of the study led the writer to conclude that, 'in short, a woman need not worry about the risk of breast cancer when facing the difficult decision of whether to terminate a pregnancy' (Hartge, 1997).

Another large cohort study was done in Sweden. It followed, for as long as 20 years beginning in 1966, 49,000 women who had had abortions before the age of 30. Not only did the study show no indication of an overall risk of breast cancer after an induced abortion in the first trimester, but it also suggested that there could well be a slightly reduced risk. Among women who had given birth prior to induced abortion, the relative risk for breast cancer was 0.58; for those who had never given birth, the relative risk was 1.09; for the total sample the relative risk was 0.77 (Lindefors Harris et al., 1989).

In 2004, an international collaborative analysis of data about 83,000 women with breast cancer who were involved in 53 studies that took place in countires with liberal abortion laws found that pregnancies that end in either induced or spontaneous abortion do not increase a woman's risk of developing breast cancer (Collaborative Group.., 2004).

Cited references
ACS- American Cancer Society. (2003, accessed 2004, February 4th) Can Having an Abortion Cause or Contribute to Breast Cancer? (online)
ACOG- American College of Obstetricians and Gynaecologists. 'Committee Opinion: Induced Abortion and Breast Cancer Risk', Obstetrics and Gynaecology, 102, 433-435.
Brody, Jane E (1997, Jan 9). 'Big Study Finds No Link in Abortion and Cancer' New York Times p. A12
Collaborative Group on Hormonal Factors in Breast Cancer. (2004, March 27). 'Breast Cancer and Abortion: Collaborative Reanalysis of Data from 53 Epidemiological Studies, including 83,000 women with Breast Cancer from 16 countries.' The Lancet 363, 1007-1016.
Hartge, Patricia. (1997). 'Abortion, Breast Cancer and Epidemiology.' New England Journal of Medicine, 336(2), 127-128.
Lindefors Harris, Britte-Marie, et al. (1989). 'Risk of Cancer after Legal Abortion during First Trimester: A Swedish Register Study.' British Medical Journal, 299(December 9) 1430-1432
Melbye, Mads, et al. (1997). 'Induced Abortion and the Risk of Breast Cancer'. New England Journal of Medicine, 336(2) 81-85.
NCI-National Cancer Institute. (2003, accessed 2004, February 4). Summary Report: Early Reproductive Events and Breast Cancer Workshop (Online).
http://cancer.gov/cancerinfo/ere-workshop-report
Querido, Melissa. (1999). 'State of the States: A Selection of Legislative Initiatives around the Country.' Reproductive Freedom News, 8(3), p.3
Simon, Stephanie. (2002, March 24) 'Abortion Foes Seize on Reports of Cancer Link in Ad Campaign.' Los Angeles Times.
Slobodzian, Joseph A. (1999, April 1). 'Philadelphia Transit Authority, Religious Group Settle over Pulled Ads.' Philadelphia Inquirer.
Westhoff,Carolyn. (1997) 'Abortion and Breast Cancer: Good Data at Last.' IPPF Medical Bulletin. 31(2), 1-2.