'We inject a sperm into every one of these cells,' Markus Montag explains. 'Then it takes more than 26 hours until the plasmosomes of the ovum and sperm cell fuse and an embryo forms. In this time frame we have to decide which of the fertilised ova to insert into the uterus.’ The reason for this is that the German law for the protection of embryos lays down that only a maximum of three fertilised ova are allowed to be implanted per attempt. 'We even restrict ourselves to only two, in order to exclude the possibility of births of triplets,' Markus Montag explains. With pregnancies involving multiple births there is an increased risk of miscarriages and malformations.
Choosing the 'best' ova
Which of the fertilised ova are finally implanted has usually been left up to chance. But today it is known that not all ova have the same quality. Using a special procedure the Bonn scientists can select the two most suitable candidates. 'For this we observe the ovule integument under a DIC microscope,' Dr. Montag explains. 'There it appears as a luminescent orange-red ring. The brighter this ring is and the more uniformly it shines, the greater the chance that it becomes a child.' The reason for this is that the ovule integument always seems to have a particularly uniform structure if the cell has matured under good conditions.
Normally every third ICSI is successful. But if medics used two 'good ' ova in their experiment, this rate increased to more than 50 per cent. With a 'good' and a 'bad' ovum the success rate was still around 40 per cent, using two 'bad' ones only 20 per cent. 'Mind you, two “good” ova are rare,' Markus Montag emphasises. 'Only with two out of ten cells does the ovule integument have an intense regular orange colour.'
Under natural conditions insemination takes place in the oviduct. After that the ovum begins to divide, while contractions of the oviduct transport it to the uterus. This process takes just under 2-3 days. When the embryo lodges in the endometrium on the sixth day after insemination, the embryo consists of several hundred cells. During the whole process the embryo is protected by the ovule integument.
The Bonn team led by Dr. Markus Montag and Professor Hans van der Ven has developed software in conjunction with the Octax Microscience Company, which analyses the image from the microscope objectively and proposes the most suitable cells. 'This way the procedure can be implemented in clinical routine without problems and without much effort,' he says.
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Images accompanying this press release can be found on the internet at http://www1.uni-bonn.de/pressDB/jsp/pressemitteilungsdetails.jsp?detailjahr=2008&detail=033 |
