To evaluate the importance of blastocyst morphology in known euploid blastocysts.
Retrospective study in a private assisted reproductive technology program.
MATERIALS AND METHODS:
The euploid status of blastocysts considered to be of marginal morphology was compared to that of good morphology blastocysts following trophectoderm biopsy and preimplantation genetic screening (PGS). Over a period of 9 months, 683 blastocysts of marginal and good quality were selected for trophectoderm biopsy and aneuploidy screening. All embryos were cultured in Continuous Single Culture Media (Irvine Scientific) to the blastocyst stage. On Day 3 of embryo development, multi-cell embryos were artificially hatched by laser ablation of the zona pellucida. Hatching blastocysts with a differentiated inner cell mass and trophectoderm were biopsied on either Day 5, 6 or 7 of culture. Biopsied embryos were categorized by morphology grade. The embryo grading scheme used in our laboratory is an adaption of the Gardner Grading Scale where AA is best quality and ED is poor quality. Blastocysts that had a grade of CC or better (ie. C or better for both the inner cell mass and trophectoderm) were placed in the good morphology group (Group 1), whereas marginal quality blastocysts (Group 2) were graded as CD, EC, or ED. Biopsied samples were analyzed by comprehensive chromosomal screening (CCS) involving the use of array comparative genomic hybridization (aCGH) or next generation sequencing (NGS) technology by a reference laboratory. Biopsies which resulted in no signal were excluded from the study. All age groups were included.
Of the 683 embryos, 554 were categorized into Group 1, while 129 were categorized into Group 2. Group 1 embryos had a normal ploidy rate of 44% compared to 34% for Group 2 blastocysts. Statistical analysis by Chi-Square demonstrated no statistical difference (p > .05 ) between the euploid rate of Group 1 and Group 2 embryos.
Recent studies have suggested that all poor morphology and slower growing blastocysts should be biopsied to determine euploid status and therefore implantation potential (Capalbo, 2014). Our results indicate that marginal quality blastocysts are capable of being euploid at a comparable rate to good quality embryos and should therefore be considered for trophectoderm biopsy and PGS. Further evaluation of the implantation potential of euploid marginal and good quality blastocysts is currently ongoing. Determination of implantation rates of marginal quality euploid blastocysts will take time, as typically the best morphological grade blastocysts are prioritized for transfer. Regardless, these findings suggest that the morphologic criteria used by most IVF laboratories in determining biopsy suitability for blastocysts may need to be reassessed in order to afford patients an optimal opportunity for pregnancy per IVF retrieval.