Prolonged Eye Contact

Antichoice Claim #1: Abortion Causes Breast Cancer

Repeat it with me: abortion does not cause breast cancer.

According to the National Cancer Institute at the National Institutes of Health:

The relationship between induced and spontaneous abortion and breast cancer risk has been the subject of extensive research beginning in the late 1950s. Until the mid-1990s, the evidence was inconsistent. Findings from some studies suggested there was no increase in risk of breast cancer among women who had had an abortion, while findings from other studies suggested there was an increased risk. Most of these studies, however, were flawed in a number of ways that can lead to unreliable results. Only a small number of women were included in many of these studies, and for most, the data were collected only after breast cancer had been diagnosed, and women’s histories of miscarriage and abortion were based on their “self-report” rather than on their medical records. Since then, better-designed studies have been conducted. These newer studies examined large numbers of women, collected data before breast cancer was found, and gathered medical history information from medical records rather than simply from self-reports, thereby generating more reliable findings. The newer studies consistently showed no association between induced and spontaneous abortions and breast cancer risk.

In addition, in a fact sheet titled Reproductive History and Breast Cancer Risk they reiterate:

 A few retrospective (case-control) studies reported in the mid-1990s suggested that induced abortion (the deliberate ending of a pregnancy) was associated with an increased risk of breast cancer. However, these studies had important design limitations that could have affected the results. A key limitation was their reliance on self-reporting of medical history information by the study participants, which can introduce bias. Prospective studies, which are more rigorous in design and unaffected by such bias, have consistently shown no association between induced abortion and breast cancer risk (18–23). Moreover, in 2009, the Committee on Gynecologic Practice of the American College of Obstetricians and Gynecologists concluded that “more rigorous recent studies demonstrate no causal relationship between induced abortion and a subsequent increase in breast cancer risk” (24). Major findings from these recent studies include the following:

 Women who have had an induced abortion have the same risk of breast cancer as other women.

Women who have had a spontaneous abortion (miscarriage) have the same risk of breast cancer as other women.

Cancers other than breast cancer also appear to be unrelated to a history of induced or spontaneous abortion.

The American Cancer Society had this to say on the matter:

The largest, and probably the most reliable, 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 of this study and the manner in which it was done provide good evidence that induced abortion does not affect a woman’s risk of developing breast cancer.

Another large, prospective study was reported on 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.

Again, 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.

The California Teachers Study also reported on more than 100,000 women in 2008. Researchers asked the women in 1995 about past induced and spontaneous abortions. While the women were being followed in the study, more than 3,300 developed invasive breast cancer. There was no difference in breast cancer risk between the group who had either spontaneous or induced abortions and those who had not had an abortion.

Further reading:

National Cancer Institute’s Early Reproductive Events and Breast Cancer Workshop summary report.

The Society For Obstetrics and Gynecology of Canada joint committee opinion.

The Canadian Cancer Society

The New England Journal of Medicine: Induced Abortion and the Risk of Breast Cancer.

National Abortion Federation fact sheet: Abortion and Breast Cancer.

The American Congress of Obstetricians and Gynecologists (ACOG) news release: ACOG Finds No Link Between Abortion and Breast Cancer Risk.

Reeves GK, Kan SW, Key T, et al. Breast cancer risk in relation to abortion: results from the EPIC study. International Journal of Cancer 2006; 119(7):1741–1745. 

Michels KB, Xue F, Colditz GA, Willett WC. Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study. Archives of Internal Medicine2007; 167(8):814–820.

Beral V, Bull D, Doll R, Peto R, Reeves G. 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(9414):1007–1016.

Henderson KD, Sullivan-Halley J, Reynolds P, et al. Incomplete pregnancy is not associated with breast cancer risk: the California Teachers Study. Contraception 2008; 77(6):391–396.

Lash TL, Fink AK. Null association between pregnancy termination and breast cancer in a registry-based study of parous women. International Journal of Cancer 2004; 110(3):443–448.

Rosenblatt KA, Gao DL, Ray RM, et al. Induced abortions and the risk of all cancers combined and site-specific cancers in Shanghai. Cancer Causes and Control 2006; 17(10):1275–1280.

Committee on Gynecologic Practice. ACOG Committee Opinion No. 434: induced abortion and breast cancer risk. Obstetrics and Gynecology 2009; 113(6):1417–1418.