When I blogged last week about TV host Guiliana Rancic’s breast cancer diagnosis in between rounds of in vitro fertilization, I asked a leading fertility specialist if Rancic’s cancer could have been caused by the IVF. Dr. Eric Widra, affiliated with the American Society of Reproductive Medicine, told me there’s no evidence to suggest that the procedure or the hormones given before—to stimulate ovaries to produce multiple egg-containing follicles—increases the risk of breast cancer.

What about ovarian cancer? I asked. On that one Widra hedged and said studies weren’t definitive to ascertain either way whether infertility procedures increased the risk of ovarian cancer; that’s because infertile women in general have a slightly higher risk of ovarian cancer compared to women who go through pregnancy and childbirth, so it’s tough to determine whether it’s the infertility or the procedure to overcome it that raises her risk.

But in a new Dutch study, researchers attempted to answer that question comparing ovarian cancer rates in nearly 20,000 women who received IVF with about 6,000 infertile women who had not. Those who had IVF had about double the likelihood of being diagnosed with ovarian cancer compared to those who didn’t over the course of the 15-year study which was published in the journal Human Reproduction.

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Most of the tumors detected, though, were “borderline” ovarian tumors that required surgery to remove the ovary but usually weren’t life threatening. The researchers also found that the increase in risk wasn’t dependent upon the number of IVF cycles women received or the dose of follicle stimulating hormones they were given.

I asked Widra for his thoughts on the study, and he said it shouldn’t deter women from having IVF, nor does it mean they should be more closely monitored for ovarian cancer. (There’s, unfortunately, no reliable screening test for the cancer; ultrasound and a blood test to measure the marker CA-125 haven’t been shown to save lives.)

Widra pointed out that the absolute risk of getting diagnosed with an ovarian tumor was very small: 0.71 percent for women who had IVF and 0.45 percent for those who didn’t. What’s more, the study doesn’t prove that IVF led to the extra cancers since it merely compared women who chose to have IVF against those who chose not too.

Some other factor could have accounted for the difference—especially since the risk didn’t continue to rise in those who had higher hormone doses on each attempt or who had IVF five or more times.

But Widra isn’t ready to dismiss the association between IVF and ovarian cancer either. In an email he wrote, “We must remain watchful for long-term consequences of all medical treatments, including IVF.”