Nurture is as important as nature when it comes to IVF, scientists have found, after showing that the chemical 'soup' in which embryos are placed during their first days of life is crucial to their success.
In a study which will be presented at the British Fertility Society meeting in Edinburgh today, experts found that by simply switching the conditions in which fertilised eggs live before implantation the womb, they can double the number of healthy embryos.
Previously it was thought that all genetic problems in embryos stemmed from DNA errors in the egg and sperm of the mother and father, and could not be altered.
But the new study proves that chromosomes - which hold the DNA - are still malleable even after fertilisation and the environment they live in has a huge impact on how well they will form, and ultimately the health of a baby.
Pregnancy loss was 3.5 times higher for embryos which grew in one ‘soup’ compared to the other.
Dr Stuart Lavery of IVF Hammersmith, part of Imperial NHS Healthcare Trust, who carried out the research at Boston Place Clinic in London said: “There has been a lot of interest in the environment in which embryos develop, and we know it can impact the birth weight and health of babies.
“But we didn’t know that it was actually having an impact on chromosomes. It seems that the embryos are actually growing differently depending in which culture medium they are placed, which is quite a big thing.
“We now need to do more work and look at exactly what factors are influencing the outcome, whether it is ph levels or something else.”
During IVF a woman’s eggs are harvested and implanted with sperm which triggers cell division and begins to form an embryo. Those embryos are monitored for several days before being implanted in the mother.
More than half of embryos don’t have the right number of chromosomes needed for a successful pregnancy and scientists always thought it was triggered by errors in the DNA of the egg, sperm or both.
But the new research showed that the number of embryos with the correct genetic make-up could be doubled by switching the culture conditions.
In the world’s largest study more than two thousand fertilised eggs were analysed over a year. Half were exposed to a newly developed EU approved culture medium whilst the other half were exposed to an established culture medium in the IVF world market. After five days the embryos were analysed and more than three hundred underwent genetic testing.
The first culture resulted in 29 per cent of embryos with the normal number of chromosomes, whilst the control culture achieved half this figure, with only 16 per cent of embryos with a viable number of chromosomes.
It similarly impacted pregnancy rates, with the second culture seeing increased early pregnancy loss, associated with chromosomal abnormalities, 3.5 times higher than the first culture environment.
There is currently no uniform regulation of embryo culture media and fertility clinics select media according to their own preferences, as long as they are EU certified.
The study also has implications for natural pregnancy, because it suggests that if conditions are not right within the womb, then a growing embryo develop genetic abnormalities.