High cholesterol levels may impair fertility in couples trying to achieve a pregnancy, researchers at the U.S. National Institutes of Health (NIH) said Tuesday.

"From our data, it would appear that high cholesterol levels not only increase the risk for cardiovascular disease, but also reduce couples' chances of pregnancy," first author Enrique Schisterman of the National Institute of Child Health and Human Development, part of the NIH, said in a statement.

Cholesterol is a waxy, fat-like substance found in all cells of the body. It's used to make a number of substances, including hormones and vitamin D. High blood cholesterol levels typically do not cause any signs or symptoms, but can increase the chances for heart disease.

For the current study, the researchers studied 501 couples who were not being treated for infertility but who were trying to conceive a child between 2005 and 2009.

The women taking part in the study ranged from 18 to 44 years of age, and the men were over 18. The couples were followed until pregnancy or for up to one year of trying.

Among the couples, 347 became pregnant over the course of the 12-month study. Fifty-four couples did not conceive a child. A hundred couples withdrew from the study, including some whose plans to have a child changed.