Frozen IVF babies at ‘double risk’ of childhood cancer
BABIES born from frozen embryos may be at increased risk of cancer, research suggests.
A study of more than a million children found that those born via frozen IVF transfer were more than twice as likely to develop childhood cancer than those born via natural birth.
The babies were most at risk of developing leukaemia and tumours of the nervous system.
There was no increased cancer risk for IVF babies born using fresh embryo transfer, the study found.
Scientists stress that the absolute risk is still tiny, with only two cases of cancer for every 500 children who began life as frozen embryos. For every 500 born via natural birth or fresh embryos there was one case.
British fertility experts believe families who have had babies by the frozen method have little to worry about. They say the numbers are so small that the findings could be down to random chance.
But the scientists behind the research, from the Danish Cancer Society Research Centre in Copenhagen, insist the difference is large enough to warrant further study.
Frozen embryos are used in 34 per cent of IVF cycles in the UK when women freeze ‘spares’ to use later or to delay pregnancy.
The study tracked 1.1million babies born in Denmark between 1996 and 2012, following them for an average of 11 years.
The scientists believe the extra risk is linked to the way freezing induces changes that may affect the way the child grows in the womb. Another possible cause
‘Caution is needed with this technique’
they suggest is the use of hormones during pregnancy.
Children born from frozen embryo transfer are at a higher risk of growing more quickly than normal, which has itself been linked to increased risk of child cancer. However, British experts point out that freezing and thawing techniques have vastly improved in recent years, so the findings may not apply to modern IVF cycles.
Professor Abha Maheshwari of the University of Aberdeen said of the study, published in the JAMA medical journal: ‘There is no reason to panic but what it highlights is that we need more data on frozen embryo transfer and should be cautious in using it for all.
‘There are pros and cons with frozen transfers, and they have to be taken in consideration with individualised decisions made for each case rather than a blanket policy of freeze all for all.’
Dr Gill Lockwood, medical director at Care Fertility Tamworth in Staffordshire, said: ‘Fortunately, childhood cancer is very rare so with even a doubling of a tiny number it still remains rare, much rarer than illnesses caused by genetic problems which affect two per cent of all pregnancies.
‘Paternal smoking has also been shown to almost double childhood cancer rates in spontaneous conceptions.’
Dr Lockwood added: ‘Modern freezing techniques like vitrification – “flash freezing” – are biologically very different than the “slow freezing” techniques which were used for most of the period that this study covers.’