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Association between embryo freezing and cancer risk in children

16 December 2019
Appeared in BioNews 1028

Children born from IVF using frozen embryos may have a slightly higher chance of developing childhood cancer, though the overall risk remains low.

Researchers analysed the rates of childhood cancers in a cohort of over one million children born in Denmark between 1996 and 2012. Of those, 3356 were conceived using frozen embryo transfer, where embryos are frozen after fertilisation and later thawed before being transferred to the woman's uterus. Across all births, they found that childhood cancer was very rare, with 2217 children diagnosed with cancer in total – a rate of around 1 in 500. This rate approximately doubled for the children born following frozen embryo transfer, of whom 14 developed cancer. 

The authors of the paper published in the Journal of the American Medical Association emphasise that their findings are 'considered exploratory' and 'should be interpreted with caution'. 

'It is important to stress the fact that the increased risk is very small for the individual as childhood cancer is very rare,' said first author, Dr Marie Hargreave from the Danish Cancer Society Research Centre in Copenhagen, Denmark.

The most frequently developed cancers were leukaemia and sympathetic nervous system tumours, which are among the most common types of childhood cancer. The authors did not find any association between IVF using fresh embryos and increased prevalence of childhood cancers. They propose 'the freezing and thawing of embryos, use of cryoprotectants [chemicals used to protect the embryos during freezing], and dissimilar protocols for the use of fertility drugs' as possible explanations for the difference. 

'It should also be noted that [during] the time period that relates to this study [an] older method of freezing was used,' said Professor Abha Maheshwari, honorary professor and director of Aberdeen Fertility Centre, University of Aberdeen, who was not involved in the study. 'Freezing techniques have improved so much in recent years, so this may not apply with newer techniques.'  

Professor Daniel Brison, scientific director of the department of reproductive medicine at the University of Manchester, who was not involved in the study also pointed to a recent UK study which showed that 'frozen embryo transfers are also associated with potential health advantages such as birth-weight and early child growth patterns which are closer to naturally conceived children.'

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HAVE YOUR SAY
Comment ( - 04/01/2020)
I agree that freezing techniques have improved so much in recent years. And maybe nowadays specialists know how to freeze biomaterial better… Anyway previous warnings concerning the use of fresh and frozen material during IVF have stayed in memory) I know some information about eggs cryopreservation, but I guess with the embryo is the same situation. And results of previous studies confirmed the fact that cryopreservation technique is effective for women who need it for medical reasons cannot be used widely to plan pregnancy. As I read the main reason for failure results of IVF programs with frozen material is poor quality of cells after their thawing. IVF with cryopreserved eggs resulted in fewer live births. Therefore it’s much better to use fresh oocytes in order to reach successful pregnancy and live birth. During cells’ thawing their structure is damaged and it is very bad. In addition not all cells survive but only some of them. And doctor can even not to see deformation of cells immediately, but in future it could lead to various diseases and abnormalities of child. I think that the same situation can be seen with the embryo freezing. Maybe some damages in structure cause serious diseases in future. Women and couples freeze own eggs or embryos in order to postpone fertility, and to have a kind of guarantee. In addition success also depends on the age of cells, health, the number and quality of eggs frozen, and the quality of the IVF lab where the procedure takes place.
Comment ( - 04/01/2020)
In the recent years, an increasing number of women have used donated eggs for the IVF procedures. It can be seen and heard donor eggs’ popularity has been growing from year to year. And I know that many European countries buy donor cells in Ukraine to carry out IVF programs at home! Ukraine was recognized as one of the best donor cells producer and therefore it sells cells. It is because there this procedure is legal and there is a low living standard in Ukraine. Egg donation programs make thousands of young, healthy women possible to sell clinics own qualitative cells for infertile couples from Europe. And thus they can earn some needed money for themselves in such way. And as of infertile women there is not always an opportunity to use fresh, not frozen eggs during IVF program. Advertising articles assures us vitrification or eggs’ freezing is a modern technique that allows specialists to save eggs and postpone indefinitely fertilization process. But what is the quality of biological material after it’s unfreezing?  Today European states where IVF is allowed actively use frozen eggs which they often buy in other countries. Egg donation is allowed not anywhere and especially it concerns commercial donation. And if it is legal there are not too many those wishing to share their cells. Therefore Europe buys donor eggs, for example, in Ukraine and it is good variants for many fertility clinics. There such procedures are clearly defined in the local legislation, and there are many young healthy women ready to give their eggs for the certain fee.
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