First author Enrique Schisterman, chief of the Epidemiology Branch at the Eunice Kennedy Shriver National Institute of Child Health and Human Development and colleagues at the University at Buffalo and Emory University in Atlanta said couples in which both partners had a high cholesterol level took the longest time to reach pregnancy and had the lowest odds of conceiving.
The study, published in The Journal of Endocrinology and Metabolism, also found couples in which the woman had a high cholesterol level, but the man did not, also took longer to achieve pregnancy.
The researchers studied couples -- 501 couples from four counties in Michigan and 12 counties in Texas from 2005 to 2009 -- who were not being treated for infertility but who were trying to conceive a child. Women were ages 18 to 44 and men age 18 and older. The couples were tracked until pregnancy or for up to one year.
Free cholesterol measurement is used in research, and differs from the cholesterol test given in doctors' offices. Tests by physicians measure the cholesterol subtypes: high-density lipoprotein, the "good" cholesterol; low-density lipoprotein, the "bad" cholesterol and triglycerides, but the researchers used the total amount of cholesterol in the blood.
The researchers theorized blood cholesterol might be related to fertility as the body uses cholesterol to manufacture sex hormones such as the male hormone testosterone and the female hormone estrogen.