Breast cancer is the most common cancer among women, other than skin cancer. In 2004, approximately 215,990 women in the US will be diagnosed with invasive breast cancer and about 40,110 women will die from the disease.

Hormonal factors play a role in a woman’s risk for breast cancer. For example, women whose bodies are exposed to higher levels of estrogen over longer periods of time seem to be at a slightly higher risk for breast cancer. This means that women who have had one or more children have a slightly lower risk of breast cancer than women who have had no children or who had their first child after age 30. But what about women whose pregnancies did not result in a live birth (ie, women who underwent either a spontaneous or an induced abortion)?

In an effort to answer this question, a group of researchers set out to gather worldwide epidemiological evidence on the possible relationship between breast cancer and abortions. The results of their study were published in the March 27th issue of The Lancet. They found that ending a pregnancy, whether through spontaneous or induced abortion, did not increase a woman’s risk for breast cancer.

About the Study

The researchers collected data on 83,000 individual women, all of whom had been diagnosed with breast cancer. This data came from 53 epidemiological studies conducted in 16 different countries where abortion was legal. They compared the odds of developing breast cancer between women whose pregnancies had ended in either a spontaneous or an induced abortion with those who had never been pregnant.

The Findings

The researchers found that the chances of developing breast cancer among women who reported having one or more spontaneous abortions was about the same as those who had never been pregnant. The same was true for women who reported having one or more induced abortions.

How Does This Affect You?

The researchers found that pregnancy ending in abortion does not appear to increase nor decrease a woman’s risk of developing breast cancer. While early termination of a pregnancy does not appear to offer women the same protection from breast cancer that a full term pregnancy might, the good news is that an abortion (spontaneous or otherwise) does not increase their risk either.

Unfortunately, large, epidemiological studies such as this are prone to certain biases that more stringently designed studies are not. For example, it appears that in some of the studies used in this analysis, women who were questioned about their abortion status after being diagnosed with breast cancer tended to be more forthcoming about their history when it was presented as a possible cause of their disease. Still, the results of this study join with those of many others in finding that abortion, whether spontaneous or induced, does not appear to expose a woman to long-term health risks.