A series of studies during the past two decades suggest that the long-standing worry among women—that in vitro fertilization (IVF) carries an increased risk for breast cancer— has no merit. The most comprehensive and recent findings — published in JAMA this week — should help to put women at ease.
The study, which was conducted between 1980 and 1995, included more than 25,000 Dutch women with an average age of 32. The researchers tested various different infertility treatments, as opposed to simply comparing the women to the general population. The findings showed that breast cancer risk in IVF-treated women was not significantly different from that of both the general population and control group at age 55. The incidence of breast cancer was 3.0 percent in the IVF group vs. 2.9 percent for the non-IVF group.
Perhaps more striking was that the researchers found that there was a significantly lower risk of breast cancer in women who underwent seven or more rounds of IVF, compared with one or two cycles. Because women undergoing IVF treatments generally give birth later in life, researchers controlled for a number of factors, like the women's age, overall number of births, and number of IVF treatments. These results are consistent with eight similar small studies that were conducted in 2013.
The news ought to be comforting to women undergoing ovarian stimulation for IVF, since the procedure temporarily causes decreased estradiol and progesterone levels, in addition to the already existing hormone imbalance which is the reason behind the IVF treatments in the first place. That combination is thought to influence the risk for breast cancer, the leading form of malignancy in women.
Previous studies in younger women gave different results. A 2012 study of more than 21,000 Australian women who began IVF treatments at 24 years old or younger showed an increased risk of breast cancer. This trend was not found in women who were older than 30. And, in 2008, a retrospective analysis found a potential increase in breast cancer in IVF patients older than 40.
Overall, experts say, there is significant amount of evidence that IVF treatments do not carry an increased risk of breast cancer, which is good news for the growing number of women who seek medical help to become pregnant. In 2012, roughly 61,000 of the 3.9 million babies born in the U.S. were through in vitro fertilization, a number that has been steadily rising.