A report by JAMA showing increased risk of cancer for children born from frozen embryo transfer is a headline which has understandably been very scary for people to read. Click here for the research that has caused the fuss. However, as always, the devil is in the detail. Often beneath the headline there is more to the story. Our resident expert top consultant gynaecologist Mahantesh Karoshi gives us his perspective.

Bottom line: do not panic about this headline – here is why: 

Why couples using frozen embryos or children born from them should not panic: 

From Mahantesh’s perspective, yes this is a large and carefully analysed study. However: ‘the results presented should not alarm couples undergoing frozen embryo transfer or children born from this technique’.

Putting it in to perceptive: 

The number of cancer cases reported was very small. Only 14 in total, and so the possibility that this has occurred by chance or due to some other unknown factor is high.

Many, many variables that could play a role…

With science, medicine and research it is rarely straight forward. There are often so many different factors that can influence an outcome. Mahantesh argues that explaining and agreeing on outcome trends is very complicated in the field of assisted reproduction. He points out that there are over 200 confounders (elements that could influence a result) in this case. That is a lot of other elements in the mix that could lead to a result ie. cancer in this case. I mean how many lifestyle factors have been linked to causing cancer?!

Childhood cancer is very rare: 

Fortunately, childhood cancer is very rare. Less than one case per 10 000 births. So, with even a doubling of a tiny number, it still remains rare. To put it into perspective it is much rarer than illnesses caused by genetic problems which affect 2% of of all pregnancies. Paternal smoking has also been shown to almost double childhood cancer rates in spontaneous conceptions.

In absolute numbers: 2 in 500 babies resulting from frozen embryo transfer and 1 in 500 resulting from fresh embryo transfer has had a diagnosis of cancer in this report. The data needs replication from other parts of the world.

The technology around frozen embryo transfer has moved on a lot since this study: (1995-2015)

Mahantesh also makes the point that almost ALL aspects of freezing technology and embryo culture have changed since the study period. Importantly, freezing technology has significantly improved, particularly embryo survival rates.

The other thing to remember is that modern freezing techniques like vitrification (‘flash freezing’) are biologically very different. This is vs the ‘slow freezing’ techniques which were used for most of the period that this study covers.

Giving the other side of the argument: 

You know what they say, there are always two sides to a story:

The ability to freeze embryos has offered two substantial benefits for couples with fertility problems:

It has effectively removed the risk of Ovarian Hyper Stimulation Syndrome (OHSS). This allows babies to born ‘one at a time’ and avoid the risk of prematurity associated with multiple births.

Embryo freezing also ‘freezes in time’ the mother’s age at the point at which the embryos were created and offers the chance of later pregnancies without having to go through repeated ‘fresh’ treatment cycles. It also reduces chromosomal abnormality which comes with advancing age.

Further, there is evidence that the birthweight of babies born from frozen cycles is higher than with fresh IVF. It actually looks closer to that of babies conceived naturally. Remember, low birthweight can be associated with health problems in later life. So, in fact, frozen transfer cycles may offer lifetime health benefits.

Conclusion around risks with frozen embryo transfer? 

The association reported between frozen embryo transfer and cancer in children does deserve further research.  However, Mahantesh’s bottom line is that the results presented in the research should not alarm couples undergoing frozen embryo transfer or children born from this technique as  it is not clear cut as headlines suggest. Further, there are also many positives on the other side.

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