Day 7 blastocyst euploidy supports routine implementation for cycles using preimplantation genetic testing.

Area of Science:

• Reproductive Science
• Embryology
• Genetics

Background:

• Preimplantation genetic testing for aneuploidy (PGT-A) is crucial for in vitro fertilization (IVF) success.
• Blastocyst development timing (Day 5, 6, or 7) influences embryo viability and clinical outcomes.
• Vitrification and Next-Generation Sequencing (NGS) are standard techniques in modern PGT-A.

Purpose of the Study:

• To evaluate the clinical utility of Day 7 blastocysts by comparing their ploidy and implantation rates to Day 5 and Day 6 blastocysts.
• To determine if Day 7 blastocysts warrant biopsy, vitrification, and transfer consideration.
• To assess the impact of blastocyst development day on pregnancy outcomes.

Main Methods:

• A retrospective analysis of 1,925 blastocysts from 402 PGT-A cycles.
• Embryos cultured for up to 7 days, biopsied, vitrified, and trophectoderm samples analyzed by NGS.
• Single euploid embryo transfers were performed using Day 5 (n=145), Day 6 (n=92), or Day 7 (n=16) blastocysts.

Main Results:

• No significant differences in implantation or ongoing pregnancy rates between Day 5 and Day 6 blastocysts.
• Day 5 blastocysts had higher euploidy rates (53.5%) compared to Day 6 (40.4%) and Day 7 (35.9%).
• Day 7 blastocysts exhibited increased miscarriage/loss rates (22.2%) and lower live birth rates (43.8%) compared to Day 5/6 embryos.

Conclusions:

• Culturing to Day 7 can identify viable euploid embryos that might otherwise be discarded.
• While Day 7 blastocysts offer potential, they are associated with poorer live birth rates due to increased miscarriage.
• Extended embryo culture to Day 7 may provide select patients with additional opportunities for achieving a healthy live birth.