Vitrified Embryos Seem To Produce Healthier IVF Babies

picture-121picture-111picture-10Three new studies have provided further evidence that vitrified embryos may be better than fresh for IVF. The studies were presented at the American Society for Reproductive Medicine conference in San Francisco, US, last week. The studies indicate that using vitrified embryos rather than fresh embryos reduces the risk of stillbirth and premature delivery. The technique allows more embryos to survive the thawing process than the older and more widely used slow-freezing method. It is unclear why this is the case; there are several theories. Some experts have suggested that when fresh embryos are used women may still be
suffering from the effects of the powerful drugs that are used to stimulate the ovaries, temporarily disrupting any IVF attempt shortly afterwards. Dr Allan Pacey, from the University of Sheffield and secretary of the British Fertility Society (BFS), said: ‘These findings are really quite interesting.
It kind of defies logic to a certain extent, because the stimulation drugs and anaesthetics that are used in egg collection have worn off by the time fresh embryo transfers are done. It seems to be an issue with the formation of the placenta, but how it has an effect isn’t known.’ It has also been suggested that only the best embryos survive the cryopreservation process. 
The three large, independent studies took place in Finland, Australia and the US. The Finnish study found that babies born from fresh embryos were 35 per cent more likely to be premature and 64 per cent more likely to have a low birth weight when compared to those born from vitrified embryos. The research that took place in Melbourne, Australia, showed that 11 per cent of babies born from fresh embryos had a low birth weight, compared to 6.5 per cent of those born from vitrified embryos. They also found that 12.3 per
cent of babies born from fresh embryos were premature, compared with 9.4 per cent of those born from vitrified embryos. Also, 1.9 per cent of babies from fresh embryos died a few days after birth, compared to 1.2 per cent from vitrified embryos. Similar findings were reported in June this year from a Danish study.
Typical IVF treatment involves stimulating a woman’s ovaries with hormones to produce eggs which are then collected and fertilised in the laboratory, with one or two embryos being transplanted into the womb two
days later. The remaining embryos can be slow-frozen or vitrified, then stored, to be used later if the initial cycle fails.
The new data may provide a dilemma for IVF clinics, as although vitrified embryos seem to result in a healthier pregnancy, the actual rate is less successful. Commenting on this, Dr Pacey said: ‘Frozen embryo
transfers are not as successful as fresh ones in terms of getting a pregnancy. So it may be that we have to balance the health of children against chance of success.’



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3 responses to “Vitrified Embryos Seem To Produce Healthier IVF Babies

  1. Rick in Texas


    I wonder if the vitrification process simply strengthens DNA in some way, thus increasing the chances of a healthy child.

    Are pregnancy rates after vitrification lower because there are simply fewer embryo’s to work with or does it have something to do with how the uterus responds to the new embryo after the transfer?

    It is amazing to me that even with today’s technology, we still have so much to learn…

    Thanks for the article…

  2. goralgandhi

    It is highly unlikely that vitrification improves the health of embryos. The reason for healthier outcomes is probably positive selection of the embryos for frozen embryo replacement. Not all embryos survive the freezing and thawing procedure, only the very top quality embryos survive and you only get pregnancies in patients with many good embryos to freeze. In fact, this is the main reason for lower pregnancy rates with frozen embryo transfer (FET). As far as the uterine receptivity is concerned, it is better in women undergoing FET than fresh ones. The ovarian stimulation that patients have to go through to produce eggs could negatively influence a subsequent pregnancy, but this does not affect women using frozen embryos.

    The findings posed here are important because women are increasingly encouraged to use fewer fresh embryos — to avoid multiple births — and to freeze any others produced in the process for later use. These findings are also reassuring that FET is a completely safe procedure, which can be used even more frequently.

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