The odds of a future pregnancy for women who freeze their eggs post 40 are very slim, and is not sensible and may also prove to be risky, the UK fertility regulator has said.

According to the Human Fertilisation and Embryology Authority (HFEA), age is the key factor for egg freezing success and doctors need to inform the risks involved to women in their 40s. "If eggs are frozen below the age of 35, the chances of success will be higher than the natural conception rate as the woman gets older," it said in a statement on Wednesday.

"Where women over the age of 40 are freezing their own eggs, the likelihood of a future pregnancy is very slim and we would caution against this being a sensible option for this group of women." The most common age of women freezing their own eggs for treatment is 38, with some women freezing their own eggs into their 40s, the health body said.  Women should be cautiously optimistic about egg freezing techniques, and that we must ensure women are fully informed about what to expect, HFEA Chair Sally Cheshire said. 

"It is also important that women undergoing any type of fertility treatment are fully aware of the risks and cost involved, and the real possibility of it being successful. "Clinics have an ethical responsibility to be clear that egg freezing below the age of 35 offers women their best chance of creating their much longed for family," Cheshire added.