by Joyce Arthur (copyright © January 2002)
published in The Humanist magazine (New York), March/April 2002, Vol 62, No. 2, pp. 7-9.

March 2003: See author's postscripts for updates on the now-disproven breast cancer/abortion link.

A major weapon of the anti-abortion movement is their scare-mongering claim that having an abortion significantly increases a woman’s risk of breast cancer (the “ABC link”). This allegation is grossly deceptive and just plain false. A substantial weight of evidence counters the ABC link, and a recent international scientific consensus has rejected the link.

Unfortunately, this doesn't stop anti-abortionists from presenting the ABC link as an undisputed fact, even manufacturing the lie that half of all abortion patients will go on to develop breast cancer. This is what anxious women were advised in 1996 when they called the toll-free number on East Coast subway ads that featured the dire warning: "Women Who Choose Abortion Suffer More & Deadlier Breast Cancer!" In spite of new research that largely refutes the ABC link, almost all anti-abortion websites still trumpet the claim without reservation, and scientific-sounding advertisements hyping the ABC link have appeared in newspapers. The latest tactic is lawsuits aimed at forcing abortion providers to inform patients of the bogus ABC link. It's all part of the never-ending anti-abortion war, and although anti-abortionists want us to believe they're fighting the battle to save women, what they're really doing is turning women into frightened pawns in a strategic campaign against abortion.

Anti-abortionists promote the alleged ABC link because 17 out of 37 scientific studies that have examined the link showed a small overall increase in breast cancer risk for women who have abortions. These studies had serious flaws, however; in particular, most were older “case control” studies that suffered from a major bias—they relied on women self-reporting their abortion history. Women with breast cancer are more likely to tell the truth about past abortions, because people with serious illnesses are motivated to report their medical history accurately to facilitate their treatment and recovery. But control groups of healthy people have less incentive to report honestly, and in fact, many women keep quiet about past abortions since it's a private and sensitive issue.

It's well-established that in medical case control studies, patients tend to disclose their histories more fully than healthy control groups (a phenomenon called "recall bias"), and a recent study[1] has confirmed abortion underreporting by healthy women. In a randomly selected group of Medicaid recipients in New Jersey, only 29% of those who had a Medicaid billing for an abortion actually admitted to the abortion in a reproductive health survey. Other studies on underreporting have found that only 35% to 60% of actual abortions are reported in surveys.[2] What this means is that the detection of an ABC link by self-report studies is untrustworthy, because women with breast cancer only appear to have had more abortions than healthy women.

The best studies of the alleged ABC link are called "historical cohort" studies, because they rely on complete medical records for entire populations of women, over decades. This means researchers have accurate statistics from a large sample to calculate exactly how many women suffered breast cancer, how many had abortions, and which ones had either or both. No cohort study has shown evidence of an ABC link, at least for abortions performed in the first trimester.

The definitive cohort study on the ABC link was completed in Denmark in 1997[3], and is widely accepted as the most powerful and accurate study to date. The researchers used data from detailed government medical registries of 1.5 million Danish women, which recorded all cases of breast cancer or legal induced abortion since 1973. The researchers found zero increased risk of breast cancer for women who have abortions by the 14th week of pregnancy. (The study left open the question of whether a risk may be present for late abortions performed after 18 weeks, but the rarity of these abortions would render any such risk less problematic.)

Attempts by the anti-abortion movement to refute the Danish study have failed. Anti-abortionist Dr. Joel Brind accused the study authors of making gross errors in their research design. In response the authors said, "We find [Brind's] argument self-contradictory and based on fundamental misconceptions about the cohort design." (New England Journal of Medicine, June 19, 1997). Although the authors corrected Brind's specific misunderstandings, their rebuke failed to modify Brind's behavior—he continues to propagate the same criticisms to his exclusive audience, the anti-abortion movement.

Brind, a professor of biology and endocrinology at New York City’s Baruch College, is a tireless proponent of the ABC link. He has devoted an entire website to the issue, zealously named www.abortioncancer.com. The website says Brind “has written and lectured extensively” on this topic since 1992, but his lecturing is confined to the anti-abortion speaker circuit, and he has published only one peer-reviewed research paper[4] on the supposed connection between induced abortion and breast cancer. This 1996 paper, a "meta-analysis" study, has been heavily criticized. Brind pooled the data from 23 studies on the ABC link and came up with a 30% increase in risk. However, most of the studies he included were those flawed by reporting bias, so it was a classic case of "garbage in, garbage out". Brind's work has been supplanted by a December 2001 review of 28 studies of the ABC link by a British researcher, who concluded there was "insufficient data to justify warning women of future breast-cancer risk when counselling them about abortion."[5]

There simply is no known mechanism that would cause the alleged ABC link. Brind speculates that abortion suddenly interrupts the estrogen surge, leaving rapidly growing breast cells in an undifferentiated state and more vulnerable to carcinogens. However, this hypothesis has no empirical support. Besides, how to explain the fact that studies show no link between miscarriage and breast cancer, as anti-abortionists acknowledge? Brind claims the "raging-hormones-cut-short" problem does not affect miscarriage, since most miscarriages are caused by a lack of pregnancy hormones. Not so—the majority of miscarriages are actually caused by genetic defects in the egg/embryo, and other causes; only an estimated 10% or so of miscarriages are caused by hormonal deficiencies. This means there is probably no significant difference between the effects of miscarriage and abortion—so if miscarriage does not lead to an increased risk of breast cancer, then of course neither would abortion.

For the sake of argument, let's suppose that Brind's ABC link is real. What would it really mean? He claims that abortion may boost the risk of breast cancer by 30%, but this increase is not really that significant anyway. For example, the risk is two to three times higher (200 to 300%) for a woman whose mother or sister had breast cancer after age 50. Even this well-established risk factor is considered moderate by scientists. In comparison, the alleged ABC link barely qualifies—even if it's real, the risk is close to negligible. To put it another way, the National Cancer Institute estimates the current risk of breast cancer to be 1 in 2,525 for a woman in her 30's—if that risk was increased by 30%, it means 1 in 1,942 women would get breast cancer.

Second, correlation does not equal causation, which means some other factor could be responsible for the increased breast cancer risk, confounding the study results. For example, women with a first full-term pregnancy after age 30 face a breast cancer risk two to three times higher than women with a full-term pregnancy before age 20. If a study included many women who had aborted their first pregnancy when they were young, effectively postponing motherhood, we might find a correlation between abortion and breast cancer—but delayed childbearing would be the more probable cause of the increased risk.

Anti-abortion "researchers" are notorious for confusing correlation with causation, which is showcased by a new study, privately funded by a British anti-abortion group.[6] The "study"—by a lone author and not peer-reviewed—blames 30 years of legalized abortion for rising rates of breast cancer in some countries. Dismissed or ignored are many other probable causes that have also proliferated in the last 30 years—including delayed childbearing, smaller family size, better cancer screening methods, environmental contaminants, obesity in mid-life, and the use of oral contraceptives and hormone replacement therapy.

Many reputable organizations have released position statements or articles discounting the ABC link, and citing the Danish cohort study and other reliable studies in support. Such groups include the American Cancer Society, National Cancer Institute, National Breast Cancer Coalition, World Health Organization, Center for Reproductive Law and Policy, Alan Guttmacher Institute, Planned Parenthood Federation of America, and others. On its website, the National Cancer Institute says: "Although it has been the subject of extensive research, there is no convincing evidence of a direct relationship between breast cancer and either induced or spontaneous abortion."[7] After reviewing the research on the ABC link, the World Health Organization's online article concludes: "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."[8] Impervious to reality, however, Brind and other anti-abortionists make the preposterous claim that these groups are conspiring in a “pro-abortion cover-up” of the ABC link.

Anti-abortionists are now taking their crusade to the legislatures and courtrooms. Laws have been sponsored in about two dozen states to force abortion providers to inform patients of the breast cancer risk, and so far, two states have passed them (Montana and Mississippi). In 1999, anti-abortionists launched a "false advertising" lawsuit against a North Dakota abortion clinic for distributing a pamphlet saying the ABC link is unsupported by medical research. The case is currently before the courts, and a new suit has recently been filed by three California women against Planned Parenthood Federation of America for "misleading" women about the ABC link.

Raising the stakes even higher, a dubious lawsuit was settled in Australia in September 2001, in which the plaintiff had sued her abortion provider for not informing her of the alleged risk of "psychiatric damage" from abortion (there's actually little or no risk[9]). Tacked onto the lawsuit was the additional "failure" to warn of an increased risk of breast cancer. Settled confidentially out of court, the case highlights the disconnect between law and science. Anti-abortionists are naively touting the settlement as "proof" of the ABC link, but lawsuit settlements are the crafty negotiations of lawyers—they have nothing to do with science and are incapable of establishing scientific facts. Defendants are often pressured to settle out-of-court for expediency's sake—not because they're in the wrong.

More lawsuits like the Australia case are on the way. Behind them lies the enduring modus operandi of the anti-abortion movement—demonizing abortion providers and intimidating women out of abortions. But given the current evidence against the ABC link, it would be irresponsible for health professionals to advise abortion patients of any alleged risk. Anti-abortionists’ fear-mongering promotion of the ABC link is reprehensible as well as fanatical. Although aware that their evidence is highly disputed, anti-abortionists continue to advise women, without qualification, that having an abortion puts them at great danger of breast cancer. For a pregnant woman faced with the traumatic, life-changing decision of whether or not to have a baby, such hypocritical posturing to advance a political anti-abortion agenda is callous in the extreme.

Author's Postscript, Summer 2002: The two pending American lawsuits mentioned in the above article have both been decisively won by the defendants—the North Dakota clinic and Planned Parenthood.

Author's Postscript, March 2003: The verdict is in — the debate is over. After a review of all the evidence, the National Cancer Institute (NCI) has officially declared that abortion does not lead to a greater risk of breast cancer. In 2002, NCI removed a fact sheet from its website that said there appeared to be no link between abortion and breast cancer and replaced it with one saying the evidence wasn't clear. A scandal ensued because the revised web page was widely believed to reflect political pressure from the Bush administration. In response, NCI convened a meeting of over 100 scientific experts in reproductive health to review the data. They released their report in March 2003, concluding that according to the best scientific studies, "Induced abortion is not associated with an increase in breast cancer risk."