Austrian researchers in a retrospective study of 1259 consecutive cycles comparing outcomes of embryos transferred at day 2-3 or on day 4-5 (blastocyst stage) revealed pregnancy rates of 28% versus 44% and a take home baby rate of 17% and 34%.
The rate of multiple pregnancies was higher in the blastocyst group 34% versus 17% and this resulted in a higher incidence of preterm deliveries.
The two groups were not matched groups in that the blastocyst group had female factor causing fertility significantly more often than the 2-3 day culture group. The 2-3 day culture group typically had a higher incidence of idiopathic infertility. The authors concluded that blastocyst transfer may lead to a higher take-home baby rate but at the cost of multiple and preterm deliveries. This study was conducted at a single clinic.
Human Reproduction 2004 19(9):2097-2102;
…But there is more
In a recent Cochrane review a statistical analysis of pooled data from different trials that between day 2/3 transfer (cleavage stage embryos) and day 5/6 transfer (blastocyst stage embryos) there was no statistically significant difference between live birth rate per couple, pregnancy rate per couple, pregnancy rate per couple where fewer blastocyst than cleavage stage embryos were transferred, multiple pregnancy rate and multiple pregnancy rate where fewer blastocysts were transferred than cleavage embryos. The authors concluded that “The current evidence fails to support a widespread change of practice from cleavage stage to blastocyst stage embryo transfer in couples undergoing IVF.” Given the conflict of one centres trial results with this Cochrane review paper it may be useful to ask clinics their exact results of blastocyst transfer and specifically whether there is a true statistically significant difference between each technique.
Human Reproduction 2004 19(9):2174 and Human Reproduction, Vol. 19, No. 4, 795-807, April 2004
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25-Jul-05 Is blastocyst transfer any better?
