One persistent scare-tactic of the anti-abortion crowd for years now has been touting the supposed “link” between abortion and breast cancer. (The idea is that breast cancer is hormonally triggered, and is made more likely by hormones present at the beginning of pregnancy, and less likely by hormones triggered by childbirth. Thus, women who carry a birth to term get a wash - no net effect on their likelihood of breast cancer, while women who terminate a pregnancy get all the bad effect and none of the good.)

This is a vaguely plausible theory that suffers from a complete lack of evidentiary backing - they just made it up. However, the “Coalition on Abortion/Breast Cancer” has done a good enough job publicizing their delusion that they have made “ABC” a a linchpin of anti-choice strategies that pretend to be rooted in concern for women’s best interests. (They have also launched a movement, backed by right-wing legal foundations, to bankroll malpractice lawsuits against abortion providers on grounds that the failure to tell patients they were at risk of breast cancer if they had an abortion was a failure of informed consent. This is an attempt to intimidate providers and scare patients away from exercising their abortion rights on the basis of unfounded claims. The right-wing lawyers have essentially unlimited funds, while the doctors already face heavy malpractice premiums, so it does not matter if the lawsuits have a chance of succeeding - they accomplish their purpose just by harrassing providers.) They have garnered enough attention that they convinced over two dozen right-wing members of Congress to sign a letter demanding that the NIH investigate the so-called “ABC” effect. Which it did.

Repeated meta-studies have shown the same result: though individual studies occasionally show a positive link between abortion and breast cancer - taken as “proof” by anti-abortion activists - many more do not, and cross-study summaries show no link. The National Cancer Institute of the NIH reported that, although full-term pregnancy, especially when young, does reduce the lifetime risk of cancer, “Induced abortion is not associated with an increase in breast cancer risk”, nor are miscarriages. And just last year, an immense, 16-country meta-analytical data review in The Lancet revealed that, among women followed prospectively (from before they had had either an abortion or breast cancer), those who went on to have abortions actually had a slightly lower risk of breast cancer than the others. (This study also found that, among women with who were asked later in life whether they had previously had an abortion, there was a slightly higher risk of breast cancer among those who reported they had - but, as the researchers pointed out, this was likely due to the distorting effect of the “retrospective” study: women who had had serious health problems were likely to give a fuller health history than others, while those who had no reason to be completely frank with their doctors may have concealed prior abortions. This is the reason for prospective studies, and the likely reason for the distinct difference in results between the prospective and retrospective arms of this meta-study.) Famed breast cancer researcher Susan Love says, about the latter study in particular:

The findings from this large international study are important for two reasons. One, they should reassure women that having an abortion does not increase their breast cancer risk. Two, they loudly dispute the lobbying and public relations efforts of groups like the Coalition for Abortion/Breast Cancer Risk, who have been using the results of poorly designed retrospective studies to increase fears about abortion and breast cancer. . . .

It should now be clear that abortion does not increase breast cancer risk. The issues about abortion are serious and controversial but they are not helped by distorting science. Anyone who continues to make that claim is dangerous, irresponsible, and ignoring the evidence.

That hasn’t stopped the propagandists, however.
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