High cholesterol levels may do more than just increase the risk for cardiovascular disease: They also may affect fertility in couples trying to become pregnant, according to the findings of a study in The Journal of Endocrinology and Metabolism led by Enrique Schisterman, PhD, chief of the epidemiology branch at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) in Bethesda, Maryland.

The study focused on 501 couples from Michigan and Texas who were not being treated for infertility but were trying to conceive. The men in the study were all aged 18 years and older; the women ranged in age from 18 to 44 years. The couples were followed until pregnancy or for up to 1 year.

Schisterman and team used blood samples obtained from the participants to measure cholesterol. Their hypothesis was that serum cholesterol might have an impact on fertility because it affects hormones such as testosterone and estrogen. 

Based on the couples’ serum cholesterol concentrations, the research group calculated the probability that a couple would achieve pregnancy by using a statistical measure called the fecundability odds ratio (FOR). 

On average, high serum cholesterol levels were associated with lower FORs and longer times to pregnancy. The longest time to achieve pregnancy occurred in couples in which both partners had high cholesterol levels. 

When the woman had a high cholesterol level and the man did not, conception also took longer than for couples in which both partners had cholesterol levels in an acceptable range.