Introduction:
Preimplantation genetic diagnosis and/or screening (PGD/PGS) allow the assessment of the genetic health of an embryo before transferring it into the uterus. These techniques require the removal of cellular material (polar bodies, blastomere(s) or trophectoderm cells) in order to perform the proper genetic analysis. We report the implantation and live birth outcome of a vitrified-warmed blastocyst developed after triple biopsy and double vitrification procedures at oocyte, cleavage embryo and blastocyst stage.
Case description:
An infertile couple, with family history of β-thalassemia, searched for IVF procedure and PGD. First polar bodies biopsy with subsequent vitrification was uninformative due to meiotic crossing-over, so oocytes were inseminated after warming. Two embryos were obtained and blastomere biopsy was performed on day 3 with inconclusive results on their genetic status. Their culture resulted in one expanded blastocyst stage on day 7 that underwent trophectoderm biopsy and vitrification. This embryo showed to be normal. It was then warmed and transferred in an artificial cycle.
Discussion and evaluation:
Preconception genetic analysis by removal and analysis of the first polar body is technically possible, but the genetic information that we can obtain at this stage may be limited and the oocytes to be inseminated is not predictable. Compared to blastomere biopsy, trophectoderm biopsy has more diagnostic efficiency with respect to both chromosomal mosaicism and PCR accuracy, reducing the problems of amplification failure and allele drop out. Moreover, embryos biopsied at the cleavage stage seem to have lower implantation rate than biopsied blastocyst.
Conclusions:
This is the first case report of a live birth obtained from a three step biopsy and double vitrification procedures of a blastocyst. This case report seems also to suggest the harmlessness of all these procedures if carefully performed by a skilled biologist in an IVF lab with quality management system. Finally, our study highlight that blastocyst cryopreserved on day 7 have clinically important potential and embryos that not reach blastocyst stage on day 6 should not to be discharged because they may result in an ongoing pregnancy.