The use of IVF technologies could be storing up future health problems for children born through the technique, according to an evolutionary biologist.
Dr Pascal Gagneux, an associate professor at the University of California, San Diego, compared the situation to the junk-food 'timebomb', where it took 50 years to observe the negative effects of fast food on health.
Dr Gagneux said: 'I wouldn't rule out that [children born via IVF] could have shortened lifespans. We are engaging in an evolutionary experiment. Assisted reproduction might have a combination of biological and social consequences that people haven't considered enough.'
Speaking at the annual meeting of the American Association for the Advancement of Science (AAAS) in Washington, DC, Dr Gagneux said one of his main worries is that, in bypassing selection processes in the female reproductive tract, defective sperm cells are not identified during fertilisation.
'The choice of the sperm is made by a technician, not by the female physiology. The concern is that by bypassing female choice at the level of sperm selection, we might produce embryos that contain risk factors that we would otherwise not have.'
Dr Gagneux also raised questions over the way in which embryos are cultured prior to implantation. Typically, an embryo will be bathed in chemical compounds for around five days, during which time certain genes are 'switched on' and others are 'switched off' – a natural process known as imprinting. Yet Dr Gagneux argued that further scientific research is needed into the epigenetic consequences of using this artificial medium.
'The big question for me is: could we learn how to avoid potentially disastrous things that we are doing to these embryos because we don't know everything yet?' he said.
Many fertility experts have strongly disputed Dr Gagneux's claims.
Professor Allan Pacey of Sheffield University told the Press Association that epidemiological studies demonstrated that IVF-born babies are just as healthy as those born naturally. 'Where some differences have been observed, these are largely explained by genetic defects in the sperm of the father rather than the fact that fertilisation and embryo development occurred outside of the body,' he added.
Dr Gagneux pointed to two studies that he says support his apprehensions about IVF. This included research showing mice born via ICSI develop certain conditions as they age, such as hormonal problems and metabolic syndrome.
He also mentioned a comparative study of IVF-born and naturally born children which found that the former were more vulnerable to heart problems when subjected to altitude to mimic the effects of ageing.
But Dr Peter Illingworth, medical director of IVF Australia said Dr Gagneux was being 'highly selective in the facts he's stating'.
'It's one very small study and we've got an abundance of research that shows as IVF kids are getting older there is no difference between their health and that of naturally conceived children,' Dr Illingworth told SBS News.
Dr Geoffrey Trew, a gynaecologist from Imperial College London, also disparaged Dr Gagneux's comments, accusing the biologist of spreading worry using 'hypothetical ideas that don't bear extrapolation to what he's saying'.
'Not good, nor responsible, science,' Dr Trew concluded.