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Abortion is NOT linked to breast cancer


In the ongoing push by right-wingers in the USA to try to control women by banning the right of a woman to get an abortion, many are pushing the long-debunked trope that abortion is linked to breast cancer. This claim is not supported by any reasonable scientific evidence.

As with vaccines, anti-abortion groups are retreading old ideas to push their anti-women narrative. I think they do this because they believe that people have forgotten the vast science that debunks the breast cancer link, so their false claims might make a convincing argument against abortion.

I’m going to review most of the evidence, from credible and authoritative scientific sources, that refute the alleged link. I know that this will not end the claims, but I hope that someone will search and find this article to use in any discussion with anti-abortion types. Not that they will be convinced by actual science.

a woman holding a cardboard with message while seriously looking at the camera
Photo by Emma Guliani on Pexels.com

Background

Research into a possible link between abortion and breast cancer began in earnest in the early 1980s. Soon after that, epidemiologists and cancer researchers were pushed into a political battle where the science was more or less overshadowed by contradicting claims.

Researchers seem to be publishing contradictory articles, but most of the studies that claimed to support a link were either biased, poorly designed, or showed statistically insignificant results. As there was more interest in women’s health research during this period, more research was done to examine a potential link.

But over the past 10-20 years, more and more scientific research has shown that there is no link. And large health agencies were convinced that there was no link between abortions and breast cancer.

Evidence against a link between breast cancer and abortion

I am going to list out some of the statements and scientific evidence from large governmental health and medical organizations that have come to a scientific consensus that there is no link.

World Health Organization (WHO)

WHO reviewed the body of scientific and medical evidence that examined the link, and they published this statement in 2011:

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.

National Cancer Institute

In 2003, the prestigious US National Cancer Institute (NCI) published its review of the link between abortion and breast cancer. Basically, they found the following:

  • Epidemiological research has established that induced abortion is not associated with an increase in breast cancer risk.
  • Spontaneous abortion is not associated with an increase in breast cancer risk.

In a statement, “the NCI Board of Scientific Advisors and Board of Scientific Counselors reviewed and discussed the results of the Early Reproductive Events and Breast Cancer Workshop, and unanimously approved the Workshop findings.” In other words, there is no link.

To be fair, NCI did point out some gaps in our research (which have mostly been filled over the 20 years since this board met).

American Cancer Society

The American Cancer Society, which researches many aspects of cancer from causes to treatment, issued this statement:

The topic of abortion and breast cancer highlights many of the most challenging aspects of studies of people and how those studies do or do not translate into public health guidelines. The issue of abortion generates passionate viewpoints in many people. Breast cancer is the most common cancer in women aside from skin cancer; and breast cancer is the second leading cancer killer in women. Still, the public is not well-served by false alarms. At this time, the scientific evidence does not support the notion that abortion of any kind raises the risk of breast cancer or any other type of cancer.

American Congress of Obstetricians and Gynecologists

The American Congress of Obstetricians and Gynecologists (ACOG) published this statement in 2009:

The Relationship between induced abortion and the subsequent development of breast cancer has been the subject of a substantial amount of epidemiologic study. Early studies of the relationship between prior induced abortion and breast cancer risk were methodologically flawed. More rigorous recent studies demonstrate no causal relationship between induced abortion and a subsequent increase in breast cancer risk.

Best research on link between breast cancer and abortion

The largest, and probably the best, study on this topic was done during the 1990s in Denmark, a country with very detailed medical records on all its citizens. In this study, all Danish women born between 1935 and 1978 (a total of 1.5 million women) were linked with the National Registry of Induced Abortions and with the Danish Cancer Registry. All of the information about their abortions and their breast cancer came from registries – it was very complete and was not influenced by recall bias.

After adjusting for known breast cancer risk factors, the researchers found that induced abortion(s) had no overall effect on the risk of breast cancer.

The size and methodology of this study provide powerful evidence that induced abortion does not affect a woman’s lifetime risk of developing breast cancer.

Another large cohort study was published by Harvard researchers in 2007. This study included more than 100,000 women who were between the ages of 29 and 46 at the start of the study in 1993. These women were followed until 2003. Because they were asked about childbirths and abortions at the start of the study, recall bias was unlikely to be a problem. After adjusting for known breast cancer risk factors, the researchers found no link between either spontaneous or induced abortions and breast cancer.

A European cohort study that published findings in 2006 followed over 260,000 women from 9 countries over an average of more than 6 years. This study found no link between induced abortion and breast cancer risk.

Summary

Respected cancer and health organizations have all come to the same conclusion — there is no link between abortion and breast cancer. And the best, highest quality large studies have shown the same thing.

This trope pushed by women’s health opponents is just one of those claims to support the anti-abortion narrative. It is false and is unsupported by any clinical evidence.

Citations

Michael Simpson
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