Fertility treatment such as in-vitro fertilisation (IVF) may not be tied to an increased risk of cancer despite the hormones used, said a study from Sweden.

Some previous studies had suggested that fertility drugs might be linked with breast, uterine and ovarian cancers.

In research reported in "Human Reproduction," Bengt Kallen of the University of Lund in Sweden and his colleagues analysed registry data from 1982-2006 on 24,000 women who gave birth after IVF, comparing rates of cancer in these women and in 1.4 million women in the general Swedish population who also gave birth in those years.

Fewer than 2% of women in the IVF group developed one or more cancers during an average follow-up period of 8 years, compared to close to 5% of the other group.

After accounting for maternal age, the number of previous pregnancies and smoking status, the overall risk of cancer was about 25% lower for women who had IVF.

"A couple who needs IVF does not have to be afraid that the hormone treatment used -- at least those used in Sweden -- will carry a risk for the woman to develop cancer," Kallen told Reuters Health.

While the risk of ovarian cancer was more than twice as high in the women who had IVF as those who didn't, Kallen suggested that this may be due to abnormalities in ovarian function that could both increase the risk for cancer and the risk for infertility, thus the need for IVF.

"The risk for two common cancers, breast and cervical, was significantly lower than expected," he said.

He addd that this might be due to women who get IVF being healthier than average or, more likely, that IVF-treated women may undergo more cervical and mammography exams.