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Blastocyst Transfer August 2003 Welcome This case discussion considers background to the use of blastocyst transfer by a couple who have otherwise been unable to conceive, using embryos transferred at an earlier stage of development (Day 3). Initial Presentation Jean is 32 years of age and she and her partner, David, have been undergoing treatment with IVF over the last fifteen months. Their infertility has been extensively investigated, but no cause has been found. Their IVF treatment has involved two stimulated cycles and three cycles during which cryopreserved embryos were transferred. On each of the five occasions, embryos of good quality (Grade 4/4) were transferred, but no pregnancy resulted. Consultant Comment Unexplained infertility affects up to 20% of couples. In vitro fertilisation allows observation of the ability of eggs to be fertilised and of the subsequent development of the embryo for up to five days. (Fig 1). Delay in the division of cells, or abnormalities in the appearance of cells, suggests an abnormality in embryo quality, usually related to premature oocyte ageing, which might be the mechanism of Jean’s infertility. In Jean’s case, a suitable number of oocytes have been obtained after stimulation and the number that fertilised in vitro appeared normal. Embryo development to Day 3 seemed normal before the embryos were transferred. However, it remains possible that subsequent development of the embryo is impaired, or that some embryos are less able to accommodate to being in the uterine environment prematurely, that is, 2 to 3 days before they would normally leave the fallopian tube. Continued culture of the embryos in a different culture media to allow further development to the blastocyst stage offers two possible benefits. Firstly, it allows selection of an embryo which has proven ability to develop thereby avoiding transfer of embryos at an earlier stage. Secondly, a blastocyst is more naturally accommodated in the uterus and is more likely to implant. Pregnancy rates after blastocyst transfer are up to 60% compared to around 30% for Day 2-3 embryo transfer (Fig 2). Jean and David discuss the possibility of having a blastocyst transfer with their clinician. This option may offer them an improvement in outcome. Jean meets the clinic’s criteria of being less than 38 years of age and having a serum FSH of <10 IU/l. Oocytes of women who do not meet these criteria are less likely to develop into blastocysts. Consultant Comment In this favourable group, approximately 50% of women will have embryos which develop to the stage of a blastocyst. Although the pregnancy rate is high in these women, there is a risk that there may be no embryos to transfer. Because of the high pregnancy rate only one, or sometimes two, blastocysts are transferred. Any additional blastocysts can be frozen, but experience has shown that blastocysts have poor survival and low pregnancy rates after thawing. In a routine IVF cycle, 90% of women will have Day 2 or 3 embryos to transfer and remaining embryos to cryopreserve (freeze) for a subsequent cycle. The cumulative pregnancy rate after transfer of fresh and frozen embryos from one stimulated cycle is around 50% per patient. In Jean and David’s case, history has shown the pregnancy rate following transfer of Day 2-3 embryos is less than normal and therefore, the odds favour culturing to the blastocyst stage before transferring. In a subsequent cycle, five Day 3 embryos were cultured in media to allow blastocyst development. One suitable blastocyst was obtained and was transferred. Jean and David are awaiting the outcome.
References Reference: Blake D, Proctor M, Johnson N, Olive D.  PRINT THIS PAGE
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