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TFC Team 2023

Day 5, 6, and 7 blastocyst ploidy status stratified by patient age


OBJECTIVE:

To determine if a relationship of ploidy status in day 5, 6, and 7 blastocysts exists amongst patient age groups.

DESIGN:

Retrospective study in a private in vitro fertilization laboratory.

MATERIALS AND METHODS:

Blastocysts underwent trophectoderm biopsy and subsequent comprehensive chromosomal screening over the course of 3 years. PGS results were retrospectively compared to the day of trophectoderm biopsy and stratified by patient age. Oocytes were fertilized using ICSI and embryos were group cultured to the blastocyst stage for up to 7 days using Continuous Single Culture Medium (Irvine Scientific). On Day 3, all multi-cell embryos were artificially hatched by laser ablation of the zona pellucida. Trophectoderm biopsy was dependent upon good quality hatching of blastocysts on either Day 5, 6 or 7 that showed a well-defined inner cell mass and trophectoderm. Biopsied blastocysts were subsequently vitrified for potential future use in a warmed embryo transfer cycle, dependent on a euploid result. Biopsied samples were analyzed by array comparative genomic hybridization (aCGH) or next generation sequencing (NGS) technology by a reference laboratory.

RESULTS:

1,915 embryos were biopsied yielding an overall euploid rate of 45% (862). Of the Day 5, 6 and 7 blastocysts, 46% (485), 46% (328) and 35% (49) were determined to be euploid respectively based on the day of biopsy. Chi-square analysis revealed that euploid status is dependent upon day of biopsy (p<0.0001). When stratified by age, a significant difference (p<0.05) in euploid rate exists between D5 & D6 and D5 & D7 blastocysts, with no significance between D6 & D7 blastocysts in patients <34 years old. Blastocysts from patients 35-37 revealed a significant difference (p<0.05) in D5 & D7 and D6 & D7 embryos but no difference between D5 & D6. No significant difference in euploid rate between day of biopsy was shown to exist in the 38-40, 41-42 and 43+ age groups.

CONCLUSION:

Aneuploidy is a very common abnormality in human embryos, particularly for women with advanced maternal age (Franasiak, 2014). Up to 61% of all embryos can be aneuploid in women who are 38-47 years old, although younger women (<35) with good prognosis also have a high rate of aneuploidy (Alfarawati, 2011; Munne, 2006). A recent report also indicates that D6 embryos have the highest euploid rate with D5 and D7 embryos contributing equally to overall ploidy status of an embryo cohort (Vaccari, 2014). Our data suggests that patients <34 have a higher rate of euploid embryos on D5 compared to D6 or D7. Day 7 embryos from patients 35-37 have the highest rate of aneuploidy. Interestingly, day of biopsy does not appear to make a significant difference in the ploidy rate of embryos from patients who are older than 38. Further investigation into the implantation and live birth rates amongst different age groups resulting from the transfer of a euploid embryo(s) biopsied on different days is currently ongoing.

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