Stimulating the ovaries to produce more eggs — a step required for in vitro fertilization — may increase the risk of developing non-cancerous ovarian tumors, according to the findings of a decades-long Dutch study.
Among women with fertility problems, those who underwent in vitro fertilization (IVF) were about four times more likely to develop a type of borderline ovarian tumor. These tumors have a very low risk of turning cancerous, and are usually removed by surgery.
Reassuringly, IVF did not increase the risk of invasive ovarian cancer, the researchers said.
It's important to note the risk of developing one of these tumors is small even for those who elect in vitro fertilization, said study researcher Flora van Leeuwen, head of the epidemiology department at the Netherlands Cancer Institute. Among the general Dutch population, women younger than 55 have a 0.45 percent chance of developing a borderline ovarian tumor, the study said. For women undergoing IVF, the risk increases to 0.71 percent – or one in 140.
More research is needed to determine whether the number of IVF cycles a woman has increases her chances of developing a tumor, van Leeuwen said.
The results will be published tomorrow (Oct. 27) in the journal Human Reproduction.
IVF and ovarian tumors
During IVF, women take fertility drugs to stimulate the production of eggs in the ovaries. The long-term effects of this process are not known.
Van Leeuwen and her colleagues analyzed medical records from more than 19,000 women in the Netherlands who underwent IVF between 1983 and 1995, and 6,000 women who did not. Women in both groups had problems conceiving children. (Women who have never been pregnant are at increased risk of ovarian tumors.)
Participants were followed for an average of 15 years.
After adjusting for factors that could affect the results, including the number of children the women already had, women in the IVF group were found to be about twice as likely to develop any kind of ovarian tumor as women in the group that did not undergo IVF. The increased risk was mostly due to a higher likelihood of developing borderline ovarian tumors.
Not a high risk
Experts say the results should not deter women from undergoing IVF.
"I am not concerned at all" about the findings, said Dr. Don Dizon, a professor of obstetrics and gynecology at Brown University's Warren Alpert Medical School.
"Family planning and having children is an important aspect of life for many women, and these findings should not detract from that," Dizon said.
Undergoing a greater number of IVF cycles did not further increase the risk of tumors for women in the study. However, this could have been because so few women in the study received a high number of treatments (six or more).
To address this issue, the researchers are expanding their study to include a larger number of women who underwent three or more IVF cycles, van Leeuwen said.
Pass it on: IVF may increase the risk of developing non-cancerous tumors, though these tumors are still not common.