Scientists have found that gene variations involved in the control of cholesterol also affect progesterone levels in women.

This new finding appears to suggest that it has an effect on how fertile a woman is.

The scientists from John Hopkins University in the USA have created a blood test that examines the variation in the SCARB1 gene. However they say that they have not, as yet, managed to develop any form of gene therapy which could improve a woman’s chance of getting pregnant.

Annabelle Rodriguez, an associate professor of medicine at the Johns Hopkins University School of Medicine told reporters: “Infertility is fairly common, and a lot of the reasons for it are still unknown.”

She added: “Right now, the benefit of this research is in knowing that there might be a genetic reason for why some women have difficulty getting pregnant. In the future, we hope this knowledge can be translated into a cure for this type of infertility.”

Ms Rodriguez and her colleagues carried out the research between November 2007 and March 2010. They analysed ovarian cells and fluid collected from 274 women who were determined to be unable to get pregnant, but who were also undergoing in vitro fertilisation.

Based on the results from this research Annabelle Rodriguez believes that gene variation is present in 8 to 13 per cent of the population.

She also found that there was a low level of progesterone in women possessing this gene variation.

Despite this research, Ms Rodriguez is hopeful that some form of gene therapy can be developed. She has been working on the development of a drug called probucol which lowered levels of cholesterol in infertile mice. The latter’s fertility was also restored.

She said: “I’m an optimist that this drug or one like it could also restore fertility in women. Everything else that was found in mice so far has borne out in humans.”