Abortion and breast cancer: a forged link

Humanist, March-April, 2002 by Joyce Arthur

A major weapon of the anti-abortion movement is its 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 it.

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-tree number on east coast subway advertisements that featured the dire warning: "Women Who Choose Abortion Suffer More and 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 ads hyping the ABC link have appeared in newspapers.

The latest tactic is lawsuits aimed at forcing abortion providers to inform patients of the bogus link. It's all part of the neverending 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 seventeen out of thirty-seven 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 sell-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 has confirmed abortion underreporting by healthy women. According to Radha Jagannatha in the November 2001 American Journal of Public Health, within a randomly selected group of Medicaid recipients in New Jersey, only 29 percent 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 percent to 60 percent of actual abortions are reported in surveys. What this means is that the detection of an ABC link by self-report studies is untrustworthy. Women with breast cancer only appear to have had more abortions than healthy women.

The best studies of the alleged 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 from which 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 conducted by the Danish Epidemiology Science Center at Statens Serum Institute in Copenhagen and reported in the January 9, 1997, New England Journal of Medicine. Researchers M. Melbye, M. Wohlfahrt, J. H. Olsen, M. Frisch, T. Westergaard, K. Helweg-Larsen, and P. K. Andersen used data from detailed government medical registries of 1.5 million Danish women, which recorded all cases of breast cancer or legally induced abortion since 1973. The researchers found zero increased risk of breast cancer for women who have abortions by the fourteenth week of pregnancy. (The study left open the question of whether a risk may be present for late abortions performed after eighteen weeks, but the rarity of these abortions would render any such risk statisically less problematic.)

Attempts by the anti-abortion movement to refute the Danish study have failed. Anti-abortionist 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." Although they corrected Brind's specific misunderstandings, their rebuke failed to modify Brind's position; 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--www.abortioncancer.com--to the issue. The website states that Brim "has written and lectured extensively" on this topic since 1992, but his lecturing is confined essentially to the antiabortion speaker circuit, and he has published only one peer-reviewed research paper on the supposed connection between induced abortion and breast cancer. This 1996 paper, "Induced Abortion As an Independent Risk Factor for Breast Cancer: A Comprehensive Review and Meta-Analysis" (Journal of Epidemiology and Community Health, October), has been heavily criticized. Brind pooled the data from twenty-three studies on the ABC link and came up with a 30 percent 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 twenty-eight studies of the ABC link by British researcher Tim Davidson, who concluded in the Lancet Oncology there was "insufficient data to justify warning women of future breast-cancer risk when counseling them about abortion."