Department of Obstetrics and Gynaecology, Medical School, University of Thessalia, 22 Papakiriazi Street, 41222 Larissa, Greece
1 To whom correspondence should be addressed. Email: messinis{at}med.uth.gr
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Abstract |
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Key words: assisted reproduction/IVF/ICSI/success rate
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Introduction |
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Low singleton rate with complications (multiple follicles) |
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High singleton rate after fetocide with complications (multiple follicles) |
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Low singleton rate after single embryo transfer (multiple follicles) |
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Low singleton rate with no complications (monofollicular development) |
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Comments and recommendations |
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A reasonable compromise is a pregnancy rate that will result in the delivery of one or two healthy babies after the 34th week of gestation. Preterm delivery is a reality that cannot be avoided even after single embryo transfer (Ericson et al., 2002) and therefore its inclusion in the statistics is inevitable. Nevertheless, differences in legislation and attitudes in different communities make it difficult for infertility experts to reach a consensus in terms of a protocol that would result in the best outcome within an IVF programme. Prospective, multicentre, randomized, controlled studies are needed to provide more data on how to improve the success of treatment and increase efficacy and safety.
Due to the various protocols for ovarian stimulation, it is evident that the expression of the results as the BESST, although easy, is not descriptive of the complete outcome of the procedure, if the intention is to define the safest but not necessarily the most effective method. Despite the fact that twin pregnancy represents a high risk factor for poor prognosis (Bergh et al., 1999; Dhont et al., 1999
), women who take part in assisted reproduction treatment are not discouraged and only 6.4% oppose the idea of twin gestation, while only 20% on average accept single embryo transfer (Pinborg et al., 2003
). The prospect of delivering a healthy baby does not seem to deter women from the associated risks. The two possibilities are to accept the current situation, i.e. singletons and multiples (mainly twins) with a pregnancy and delivery rate >20% per cycle initiated, or to agree that only single embryo transfer is acceptable with or without ovarian stimulation. In that case, efforts should be directed towards improve the implantation rate by focusing research on the endometrium. Improved outcome with IVF treatment may also be possible through improvement in culture and cryopreservation conditions. Theoretically, one could also use cloning technology, i.e. removal of blastomeres from a single embryo and generation of new individual embryos that could be transferred one at a time. The ethical issues of such an approach are very complex.
In conclusion, BESST as defined by Min et al. (2004) may not be the best outcome variable in an IVF programme. Although it is an interesting primary endpoint, it is still early for conclusions to be drawn regarding successful pregnancy in humans. The proposed methodology has several limitations that need to be addressed before IVF treatment can provide rates of singleton and multiple pregnancies similar to those of natural conceptions.
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References |
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Submitted on April 28, 2004; accepted on May 20, 2004.
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