Infertility is associated with a higher risk of developing cancer in women of childbearing age, say researchers including one of Indian-origin.

The findings, published in the journal Human Reproduction, showed that infertile women had an overall 18 per cent higher risk of developing cancer compared to women who were not infertile. 

However, the absolute risk is very low at just two per cent compared to 1.7 per cent among women who are not infertile, found researchers at Stanford University in the US.

"We do not know the causes of the increase in cancer that we found in this study, whether it might be the infertility itself, the causes of the infertility, or the infertility treatment," said lead author Gayathree Murugappan. 

"We can only show there is an association between them," she added. 

For the study, the team analysed data from 64,345 infertile women who were followed for nearly four years. 

Although breast cancer was the most common in both fertile and infertile women, the team found a slightly higher risk of hormone-driven cancers of the ovary and uterus among the infertile women. 

They also found a slightly higher risk of cancers of the lung, thyroid, liver and gallbladder and leukaemia among the infertile women. 

"While several of these associations were significant, it is important to note that the absolute increases in risk were modest," said Murugappan.

"The low overall incidence of cancer among these women means that one in 49 infertile women would develop cancer during the follow-up period compared to one in 59 women who were not infertile," said Michael Eisenberg, Associate Professor at the varsity.

Further research needs to be carried out to determine what factors may be influencing the long-term risk of cancer for infertile women, Eisenberg noted.