BackgroundHuman embryos produced by in vitro fertilization (IVF) are usually cultured to day 6 after insemination, and good quality of embryos should develop to blastocyst stage at days 5 and 6. However, some embryos develop slowly, thus they may form blastocysts on day 7. Most IVF laboratories culture embryos to day 6 and then discard retarded embryos that do not develop to blastocyst stage. It has been reported that transfer of day 7 blastocysts can yield pregnancy although the rates were very low. In the present study, we evaluated the prevalence of aneuploidy in day 7 human blastocysts and also assessed embryo implantation after transfer of normal euploid blastocysts developed on day 7.MethodsDay 7 blastocysts were biopsied and screened for aneuploidy. Embryo implantation was assessed by transferring of euploid blastocysts.ResultsA total of 1966 blastocysts from 367 IVF cycles were biopsied and screened for aneuploidy. It was found that 81.5 % of the patients had days 5 and 6 blastocysts and 18.5 % (68) patients had blastocysts developed on day 7, including 15.3 % had days 5–7 blastocysts and 3.3 % had only day 7 blastocysts. A total of 151 day 7 blastocysts, which accounted for 7.7 % of total blastocysts, were analyzed. It was found that 36.7 % of the blastocysts were euploid and 63.3 % had abnormal chromosomes, including aneuploidy and euploid with partial chromosome deletion. The aneuploidy rate was also maternal age dependent and was as high as 91.7 % in patients who were ≥40 years old. During the study period, transfer of day 7 euploid blastocysts in 15 patients resulted in 2 healthy live births.Conclusion(s)Aneuploidy rates in day 7 human blastocysts produced by IVF are very high. However, good euploid blastocysts have potential to implant and transfer of day 7 euploid blastocysts can result in healthy live birth. It is suggested that day 7 blastocyst culture may be necessary in patients who need aneuploidy screening.
BackgroundHigh proportions of human embryos produced by in vitro fertilization are aneuploidy and mosaic. DNA microarray is one of the most practical screening methods to select euploid embryos for transfer. However, mosaic pregnancy is still possible due to embryonic mosacism. Here we report a successful pregnancy after transfer of a mosaic blastocyst with euploid inner cell mass.MethodsA woman with a previous trisomy 13 pregnancy pursued infertility treatment with preimplantation genetic screening by a trophectoderm biopsy and DNA microarray. NimbleGen oligonucleotide DNA microarray was applied to biopsied samples from 13 blastocysts. A euploid blastocyst was transferred to the patient and subsequent prenatal cytogenetic tests were performed by FISH and/or G banding.ResultsFollowing DNA microarray, it was found that 5 blastocysts were euploid and 8 were aneuploidy. Transfer of one euploid blastocyst resulted in a clinical pregnancy. Prenatal cytogenetic tests of samples biopsied from chorionic villi sample showed both trisomy 21 (47 XX, +21) and euploid (46, XX) cells. Further prenatal cytogenetic test with a sample from amniotic fluid indicated that all cells were euploid (46, XX). The pregnancy was continued and a healthy girl was delivered after 41 weeks of gestation.ConclusionsThis is the first report to indicate a mosaic pregnancy after transfer of a “euploid” blastocyst that was screened by DNA microarray, and the case further confirms that mosaicism is present in human blastocysts produced by in vitro fertilization.
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