Scientists find IVF babies born from frozen embryos are at a greater risk of cancer

Children born through the use of frozen embryos may be at higher risk of cancer than children born through other methods, a large Nordic study suggests.

While the absolute number of children who actually had cancer was low, the researchers say their findings should prompt fertility clinics to veer away from a “freeze-all” approach until more is known about how freezing and thawing embryos can affect the health of future generations.

It’s estimated that nearly one in 12 children in Europe are currently born after fertility treatments, including in vitro fertilisation (IVF).

This type of assisted reproductive technology (ART) allows embryos to be created from a human egg and sperm in a laboratory, and, as early as three days later, to be transferred to the patient’s uterus.

But more and more often, IVF embryos are frozen for a few months – or years – before being thawed and implanted for pregnancy.

For their study, published in the open-access journal PLOS Medicine, researchers at the University of Gothenburg in Sweden analysed medical data from nearly 8 million children in Denmark, Finland, Norway, and Sweden.

Of those, more than 170,000 were born after the use of ART, including 22,630 born after frozen-thawed embryo transfer.

The research found that children born after frozen-thawed embryo transfer had a roughly 1.6 to 1.7 times higher risk of cancer than children born after fresh embryo transfer and those born without the help of any fertility treatment.

In absolute numbers, it’s still very few: only around 2 per 1,000 children born after a frozen embryo transfer would go on to have cancer compared to fewer than 1.5 per 1,000 children in the two other categories.

"It is in fact quite modest, this increase. And that’s quite