Unintended and unwanted consequences of IVF may emerge towards the end of the life of IVF babies, a scientist warns.
Assisted reproduction is an "evolutionary experiment" that could prove as big a health disaster as junk food, a scientist has warned.
Dr Pascal Gagneux, an evolutionary biologist from the University of California at San Diego in the US, believes the technology may be storing up serious trouble for ageing populations of IVF children.
Of the estimated five million IVF offspring alive today, the oldest of them, British "test tube baby" Louise Brown, is only 39.
Unintended and unwanted consequences of IVF that cannot be detected now may emerge towards the end of life, Dr Gagneux fears. And he points out that scientists have already uncovered ominous signs.
IVF mice that are allowed to age become ill - females develop a pre-diabetic condition called metabolic syndrome, while male animals suffer hormonal problems.
More worrying was one study which involved taking 100 IVF and naturally conceived children aged as young as six 3500 metres up a Swiss mountain, where low oxygen levels mimic effects of ageing.
Heart and artery malfunction was reported "very convincingly" in the assisted reproduction children, including those with brothers and sisters who were conceived naturally, said Dr Gagneux.
Speaking at the American Association for the Advancement of Science annual meeting in Washington DC, he said: "I'm an evolutionary biologist and interested in human origins. To me this is the epitome of a species taking its own fate into its own hands.
"We're engaging in an evolutionary experiment ... I would compare it to high fructose corn syrup and fast food in the US. It took 50 years; it was fantastic, you got bigger and healthier, and now the US are the first generation that are shorter and heavier and die younger. But it took 50 years.
"I think we can't rule out that it could be shortening life span. It could also be introducing some very interesting costs in terms of metabolic syndrome."
When nature is allowed to take its course, only a handful of sperm out of 100 million ever make it to the egg. Just one will fuse successfully with the egg and achieve the goal of fertilisation.
"What is interesting is that the force of natural selection is extremely strong early in life and becomes very weak late in life," said Dr Gagneux.
"The very reason why we age has to do with the fact that you can select for things that help you when you're young and those very same things will kill you when you're old.
"With increased life expectancy and maximum longevity, we are setting the stage so that even a slight deviation from something highly adaptive might bite you in the butt quite badly when you're 70, 80 or 90."
One of his biggest concerns was the way IVF embryos were bathed in a cocktail of chemicals for up to five days during the phase when genetic "imprinting" is taking place.
This is a process that switches on some genes, and switches off others, and it has effects that can be passed down for generations.