An alarming new study shows that children born from frozen-stored embryos are at increased risk of developing cancer.
Researchers at the University of Gothenburg in Sweden found that children born from frozen embryos in particular were at an increased risk of developing leukemia and cancer related to the central nervous system. Interestingly, the same risk was not found for children born through other assisted fertilization methods.
Births from frozen embryos are relatively rare, accounting for only a tiny proportion of all babies born using assisted reproductive technology (ART), and therefore little large-scale population data is available for them.
Over a million embryos are currently frozen in the United States, although the vast majority are never used. Penn Medicine reports that from 1987 to 2015 around a million babies were born through in vitro fertilization — although nearly all were born with a fresh embryo.
A 2017 report by the Centers for Disease Control and Prevention found that there were around 29,000 frozen embryos in the United States that resulted in a live birth in 2015.
A new study shows that children born from frozen-stored embryos are more likely to develop cancer. Those born from fresh embryos did not suffer from the same risk. Researchers are unsure why this is the case (file photo)
Researchers, who published their findings in PLOS last week, collected data from 7.9 million children in four Scandinavian countries – Denmark, Finland, Norway and Sweden – for the study.
IVF: The technology that enables thousands to start families
In vitro fertilization, known as IVF, is a medical procedure in which a woman has an already fertilized egg placed in her uterus to become pregnant.
It is used when couples are unable to conceive naturally and a sperm and egg are removed from their bodies and combined in a laboratory before the embryo is placed in the woman.
Once the embryo is in the womb, the pregnancy should proceed normally.
The procedure can be performed using eggs and sperm from a couple or from donors.
Guidelines from the National Institute for Health and Care Excellence (NICE) recommend that IVF should be offered under the NHS to women under the age of 43 who have been trying to conceive through regular unprotected sex for the past two years.
People can also pay for IVF privately, which costs an average of £3,348 for a single cycle, according to figures published in January 2018, and there is no guarantee of success.
According to the NHS, success rates for women under 35 are around 29 per cent, with the chance of a successful cycle decreasing with age.
It is believed that around eight million babies have been born as a result of IVF since the very first case, British Louise Brown, was born in 1978.
chances of success
The success rate of IVF depends on the age of the woman being treated and the cause of infertility (if known).
Younger women are more likely to have a successful pregnancy.
IVF is not usually recommended for women over the age of 42 because the chances of a successful pregnancy are considered too low.
Of this population, 172,000 were born with some type of ART and 22,630 were from a frozen embryo.
Researchers found that children born after an embryo was thawed were more likely to develop cancer at a younger age, with leukemia and cancer of the central nervous system — which usually affects the brain or spinal cord — being the most common.
On average, 2.07 out of 1,000 spontaneously born children developed cancer.
Children born from a fresh embryo — which accounts for a majority of IVF pregnancies — had a slightly lower risk of developing cancer. Researchers found that 1.97 in 1,000 developed the disease.
Those born from a frozen embryo were at highest risk, with 2.12 in 1,000 being diagnosed.
Frozen embryonic children also often suffered from their diagnosis earlier in life. The study found 30.08 cases per 100,000 life-years – almost double the rate in the fresh embryo and spontaneous birth groups.
Overall, however, the case numbers were small, and the researchers don’t think that should deter a potential family from freezing their embryos.
“The individual risk was small, while it could have implications at the population level due to the huge increase in frozen cycles after assisted reproduction,” said Ulla-Britt Wennerholm, co-author of the study, who serves as an obstetrician, reported by UPI.
“Overall, no increase in cancer was found in children born using assisted reproduction techniques.”
Researchers aren’t sure why children born from frozen embryos might be most at risk, although they have a few theories.
‘The reason for a possibly higher risk of cancer in children born later [embryo freezing] is not known,” they wrote.
“Each type of childhood cancer has its own risk factor profile, but it is believed that many childhood cancers are due to embryonic accidents and originate in the uterus.
High birth weight has been linked to a higher risk of cancer in children [changes to the DNA based on environment] have been suggested as a possible explanation.’
The number of women who freeze their eggs has skyrocketed in recent years as many in the western world have decided to put aside family building in order to pursue career goals.
In 2018, 13,000 women chose to freeze embryos, up from under 500 almost a decade earlier in 2009.