Couples with high cholesterol levels may have a harder time conceiving a child, according to a recent study CBS News reported.

Researchers found that couples who did not become pregnant during the 12-month study had higher free cholesterol -- cholesterol that is not bound to another molecule; by contrast, HDL and LDL cholesterol is bound to proteins -- levels that couples who did conceive.

"We found a relationship between high free cholesterol levels and a longer time to pregnancy in couples," Enrique Schisterman, study researcher and senior investigator at the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Rockville, Md., told Live Science. "This is the first study to look at cholesterol levels in both partners at the same time, and their influence on the probability of becoming pregnant."

For the study, researchers monitored more than 500 couples in Michigan and Texas who were trying to have a baby and were not being treated for infertility. Blood samples were collected from the participants to measure the levels of five fats: free cholesterol, total cholesterol, phospholipids, triglycerides and total lipids.

During the study, 347 couple became pregnant.

After measuring the five fat levels, researchers found a strong link between higher levels of free cholesterol in couples and their time to become pregnant.

The findings suggest that cholesterol levels may be an important factor in healthy couples who want to conceive and who don't have infertility problems, Schisterman told Live Science.

Researchers said the findings have broad public health importance because "the rate of high cholesterol levels and obesity is so high in the United States that even slight changes in the population, such as reductions in cholesterol levels or obesity rates, may affect couples' ability to become pregnant."

The findings were recently published in the Journal of Clinical Endocrinology and Metabolism.