Children born from IVF that uses frozen eggs may have a higher risk of cancer, a study suggests.
Eggs are often frozen when a woman is younger to enable her to have children later in life but with the healthier and fitter eggs of her younger self, and official guidance in the UK was updated earlier this year so that they can now be stored for 55 years.
The technique is also used so women who are ill can have children before undergoing treatment, such as chemotherapy, which can damage their eggs.
The freezing, storing and thawing of eggs can cost up to £10,000, depending on the length of time they are kept on ice, and the cost may be picked up by the NHS in the event of medical reasons.
Researchers looked at data covering almost eight million children born in Denmark, Finland, Norway and Sweden since the mid-1980s, of whom 171,000 were conceived using some form of fertility treatment.
More than 22,630 of the technology-assisted births involved frozen embryos, and scientists found that 48 of these children went on to be diagnosed with cancer before the age of 18, a rate of 30.1 for every 100,000 person-years.
In contrast, the rate of cancers for fresh embryo transfers was just 18.8 per 100,000 person-years. When accounting for all factors, the scientists say the risk of cancer is 59 per cent greater for children born from a frozen embryo procedure than a fresh embryo, and 65 per cent greater than a natural conception.