A “fertility switch” in the womb can make a woman less likely to conceive or increase her risk of miscarriage, research has shown.

High levels of the enzyme protein are linked to infertility.

However, low levels are not good either, since they increase the odds of losing a baby.

The findings, reported in the journal Nature Medicine, could lead to new fertility treatments or methods of contraception, experts believe.

Scientists from Imperial College London made the discovery after analysing womb lining tissue samples donated by 106 women being treated either for unexplained infertility or recurrent pregnancy loss.

Those from infertile women, who had been trying to conceive for two years or more, were found to have low levels of the enzyme SGK1. Conversely, women with a history of miscarriage had low levels of SGK1 in their womb lining.

Tests on mice showed that levels of the protein in the womb lining of female animals declined during the “fertility window” when they could get pregnant.

When extra copies of the SGK1 gene were implanted into their wombs, they were unable to conceive.

Jan Brosens, formerly at Imperial College and now at the University of Warwick, said: “Our experiments on mice suggest that a temporary loss of SGK1 during the fertile window is essential for pregnancy, but human tissue samples show that they remain high in some women who have trouble getting pregnant.

“I can envisage that in the future, we might treat the womb lining by flushing it with drugs that block SGK1 before women undergo IVF. Another potential application is that increasing SGK1 levels might be used as a new method of contraception.”