During the last few decades, women taking fertility drugs in order to become pregnant have not had definitive evidence that such treatments would not increase their ovarian cancer risk. Now researchers from Denmark, who conducted the largest population-based cohort study thus far to address this question, have reported that fertility drugs do not increase a woman’s risk of ovarian cancer. The study, led by Dr. Allan Jensen of the Institute of Cancer Epidemiology in Copenhagen.

The study involved 54,362 Danish women who were treated in fertility clinics between 1963 and 1998 and then followed for a median of 15 years; 156 of these women eventually developed invasive epithelial ovarian cancer.

Ovarian cancer risk was no greater for women who used any of four different groups of fertility drugs than for those who had not used these drugs. Of the ovarian cancer cases that did occur in this cohort, 58 percent were serous tumors—occurring in the outer lining of the ovary—and the incidence of this particular tumor type appears significantly higher only among women who had taken clomiphene, which was the most commonly used fertility drug. The authors noted that this association “may be real and important,” but they pointed out that long-term follow-up studies will be needed to confirm this finding. Also, because the usual peak age for ovarian cancer diagnosis is 63 and the average age of these women was only 47 by the end of the study, they will continue to monitor the cohort.

Nevertheless, “Some women who take fertility drugs will inevitably develop ovarian cancer by chance alone,” explained Dr. Penelope Webb in an accompanying editorial, “but current evidence suggests that women who use these drugs do not have an increased risk of developing ovarian cancer.”