In February 2003, the US National Cancer Institute (NCI) held a workshop of more than 100 of the world’s leading experts who study pregnancy and breast cancer risk. The experts reviewed human and animal studies that looked at the link between pregnancy and breast cancer risk, including studies of induced and spontaneous abortions. Some of their findings were:
• Breast cancer risk is increased for a short time after a full-term pregnancy (that is, a pregnancy that results in the birth of a living child).
• Induced abortion is not linked to an increase in breast cancer risk.
• Spontaneous abortion is not linked to an increase in breast cancer risk.
The level of scientific evidence for these findings was considered to be “well established” (the highest level).
The American College of Obstetricians and Gynecologists (ACOG) Committee on Gynecologic Practice also reviewed the available evidence in 2003 and again in 2009. ACOG published its most recent findings in June 2009. At that time, the Committee said, “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.”
In 2004, the Collaborative Group on Hormonal Factors in Breast Cancer, based out of Oxford University in England, put together the results from 53 separate studies done in 16 different countries. These studies included about 83,000 women with breast cancer. After combining and reviewing the results from these studies, the researchers concluded that “the totality of worldwide epidemiological evidence indicates that pregnancies ending as either spontaneous or induced abortions do not have adverse effects on women’s subsequent risk of developing breast cancer.” These experts did not find that abortions (either induced or spontaneous) cause a higher breast cancer risk.
