Children born following IVF are more likely to develop childhood cancers than children conceived naturally, according to a new study. This risk does, however, appear to be small and may result from specific postnatal factors.
The researchers, led by Dr Bengt Källén from the University of Lund in Sweden, used national birth and cancer registers to compare the number of children with cancer born following IVF with those born naturally. The study included children born between 1982 - the year the first child was born following IVF in Sweden - and 2005.
In total, 26,692 children were born following IVF in this period. The authors calculated that, under normal circumstances in a population of this size, 38 children would be expected to develop some form of cancer. The actual number of children with cancer in the IVF population was 53 - a number shown statistically to be significantly higher than expected. The cancers were mainly of the blood (including various leukaemias), the eye and the central nervous system.
Dr Källén and colleagues said: '[The increased risk] is probably not attributable to the IVF procedure itself but could be an effect of [underlying contributions] from unidentified characteristics of women who undergo IVF or could act via the widely known increased risks for [newborn] complication [in babies born following IVF]'.
'It should be stressed that the individual risk for a child who is born after IVF to develop childhood cancer is low.'
The authors looked at factors previously linked to poor health in IVF newborns to see if they were responsible for the increased cancer risk. They found that high birth weight, premature delivery, postnatal respiratory problems and a low Apgar score (a measure of general newborn health) were risk factors for childhood cancer. More common risk factors, such as the age of the mother, smoking status and multiple births, did not affect the cancer risk.
Dr. David Cohen, chief of reproductive medicine at the University of Chicago said: 'This study is interesting and thought-provoking, and it adds to our growing knowledge of potential IVF consequences'.
'But, it's difficult to think what the biological plausibility would be. If it were something that occurs during the in vitro process or some substance in the media used, I would think that it would cause a much higher number of cancers. This may just be a statistical oddity', he added.
The study is published online in Pediatrics.