Links Between Abortions and Breast Cancer Not Supported By Science

My first pregnancy ended in a miscarriage—a spontaneous abortion, the doctors called it. I was broken-hearted. I so wanted that little baby and was already in love with it. I was blessed with a beautiful son less than a year later and a gorgeous daughter two years after that.

Still, the memory of that miscarriage saddens me even now. And when I got breast cancer and came across postings that tied abortion—spontaneous or induced—to breast cancer, I thought I was being punished twice.

So I looked at the evidence. I was ready to be blamed. Don’t we always think something we did caused our breast cancer? Aren’t we always, in some place in our minds, to blame? We’re so vulnerable after a diagnosis that we are sadly open to additional wounds.

And scientific studies often look at spontaneous abortions—miscarriages like mine—in the same way they look at induced abortions. Both are terminations of pregnancy.

The studies mentioned below were comprehensive, some studying groups as large as 100,000, others looking at a multitude of other studies to search for evidence. They found no credible link between spontaneous or induced abortions and breast cancer.

Here’s what the National Cancer Institute says on the subject:

In February 2003, the National Cancer Institute (NCI) convened a workshop of over 100 of the world’s leading experts who study pregnancy and breast cancer risk. Workshop participants reviewed existing population-based, clinical, and animal studies on the relationship between pregnancy and breast cancer risk, including studies of induced and spontaneous abortions. They concluded that having an abortion or miscarriage does not increase a woman’s subsequent risk of developing breast cancer. A summary of their findings can be found in the Summary Report: Early Reproductive Events and Breast Cancer Workshop.

NCI regularly reviews and analyzes the scientific literature on many topics, including various risk factors for breast cancer. Considering the body of literature that has been published since 2003, when NCI held this extensive workshop on early reproductive events and cancer, the evidence overall still does not support early termination of pregnancy as a cause of breast cancer. To view regular updates on this topic, please go to the Breast Cancer PDQ® summary, which is part of NCI’s comprehensive database.

The American Cancer Society provides additional evidence that breast cancer is not linked to abortions. (Note: Some of the studies refer to “recall bias,” which means that women may not honestly recall their previous health histories. Some research indicates that women with breast cancer are actually more likely to honestly report having had abortions, because they are looking for something that might have caused their cancer.)

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.