Infertility has been linked to higher risk of developing certain types of cancer. A new study of more than 64,000 women of childbearing age in the U.S. shows that infertile women have 18 percent higher risk compared to those without fertility issues.  

Researchers said fertility problems lead to higher chances of developing cancers in the ovary, uterus and breast. The team also found slight increase in the risk of having lung, thyroid, liver and gallbladder cancers as well as leukemia, EurekAlert reported Tuesday

Overall, infertile women have 2 percent chances of developing any of the said conditions. The findings, published in the journal Human Reproduction, come from the analysis of health insurance claims across the U.S. that cover infertility testing and treatment. 

The researchers reviewed data from 64,345 women diagnosed as infertile from across 50 states. The team compared the data with 3,128,345 women who did not report any fertility issue in their 30s.

After nearly four years of analysis, 1,310 infertile women were found suffering from cancer, while 53,116 among the fertile group had the disease. Breast cancer was the most common cancer in both groups. 

Michael Eisenberg, senior author of the study and an associate professor at Stanford University School of Medicine, said estimates show one in 49 infertile women would develop cancer compared to one in 59 ferttile women.

The researchers suggested that giving birth provided women the protection against cancer risks. 

However, the study did not find the direct causes or link between infertility and cancer development, according to lead researcher Gayathree Murugappan, a fellow in reproductive endocrinology and infertility at Stanford University School of Medicine.

"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,” she said. “We can only show there is an association between them.” 

Murugappan’s team hopes to conduct another study in a longer period to determine the factors that may be influencing the long-term risk of developing cancer among infertile women.