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The predictive value of day 3 embryo morphology for blastocyst formation and implantation rate at day 5 in IVF. P.M. Rijnders and C.A.M.Jansen Dept of IVF,Obstetrics and Gynaecology, Diaconessenhuis Voorburg, The Netherlands The transfer of blastocysts 5 days after insemination has been associated with a very high implantation rate (Scholtes and Zeilmaker,1996). However only a minority of embryos achieve the blastocyst stage at this time. As overall pregnancy rates were similar after day 3 and day 5 transfers, it could be that the benefit obtained by a better selection does not outweigh the disadvantage of exposing embryos longer to artificial culture conditions. In addition in a number of cases a limited availability of embryos does not require a longer culture period. The key question is whether embryo morphology before expression of the embryonic genome is predictive for further development to blastocysts. Materials and Methods: A prospective study was carried out in 48 patients, with a mean of 2.8 failed transfers and with supernumerary embryos obtained in the past. The morphology of the embryos on day 3 was registered. After pre-selection of the embryos which would have been transferred on day 3, all embryos were allowed to develop further until transfer on day 5, at which time blastocysts were preferably chosen for transfer. During the culture period embryos were cultured individually. Results: Results: The clinical pregnancy rate per embryo transfer (ET) was 45 %. Of the 108 embryos 26 implanted (implantation rate of 24.1 %) of which 25 resulted in cardiac activity (23.1 %). It appeared that only 51 % of the embryos which were actually transferred, would have been selected for transfer on day 3. In all, 20 % of the transfers had total and 56 % had partial agreement with prior selection on day 3. Hence 24 % of the day 5 transfers had no agreement at all. It was worth noting that 53 % of the class 1 or 2 embryos on day 3 did not reach the blastocyst stage on day 5. In contrast 20 % of the embryos with more than 20 % fragmentation on day 3 developed into blastocysts on day 5. When blastocysts alone were transferred a clinical pregnancy rate of 50 % per transfer was observed (20 out of 40 Embryo transfers). Mixed transfers, i.e. blastocysts in combination with less developed embryos, resulted in 20 % pregnancy rate per transfer (1/5 ET). Following the transfer of non-cavitating embryos on day 5 no pregnancies were observed (none of the three embryo transfers). Conclusion: Conclusion: it is clear that the predictive value of embryo morphology before the expression of the embryonic genome is limited. Hence, there is a distinct group of patients that benefits from continuing embryo culture for a longer period. There is no need for prolonged culture when only a limited number of embryos is available. A possible disadvantage may be a decrease in the embryo survival rate after cryopreservation because of freezing at a later stage. Reference: Scholtes & Zeilmaker (1996) Fert.Steril. in press |
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