Couples with high levels of cholesterol may have a harder time conceiving.

A new study has also shown that couples in which only the woman had a high level of cholesterol and the man did not also took longer to conceive, as compared to couples in which both partners had acceptable levels of cholesterol.

Researchers at the National Institutes of Health, the University at Buffalo (New York), and Emory University in Atlanta analyzed couples who were trying to get pregnant, but not being treated for infertility. The analysis involved 501 couples from counties in Michigan and Texas from 2005 to 2009.

Participants provided blood samples that were then tested for cholesterol. These blood tests measured the total amount of cholesterol, and did not differentiate between subtypes, such as LDL, HDL and triglycerides.

The study’s first author, Enrique Schisterman, Ph.D., chief of the Epidemiology Branch at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), theorized that cholesterol in the blood might be associated with fertility considering the fact that cholesterol is used by the body to manufacture sex hormones such as estrogen and testosterone.

The researchers discovered that on average, high cholesterol levels were linked to longer times to achieve pregnancy.

“We’ve long known that high cholesterol levels increase the risk for heart disease. In addition to safeguarding their health, our results suggest that couples wishing to achieve pregnancy could improve their chances by first ensuring that their cholesterol levels are in an acceptable range,” said Schisterman in a statement.

The findings of the study are published online in JCEM.