[Pre-implantation genetic testing: Comparison between cleavage stage and blastocyst biopsy]

Area of Science:

• Reproductive Medicine
• Genetics
• Embryology

Background:

• Preimplantation genetic testing (PGT) lacks global standardization in practices.
• Biopsies are performed on day 3 or day 5 (blastocyst) embryos.
• Day 3 biopsy allows fresh transfer, while day 5 often requires embryo freezing.

Purpose of the Study:

• To compare live birth success rates in couples undergoing PGT based on biopsy timing (day 3 vs. day 5).
• To evaluate the efficiency of different biopsy strategies in the laboratory.

Main Methods:

• Retrospective monocentric study of PGT cycles from 2016-2019.
• Comparison of outcomes between day 3 and day 5 embryo biopsy groups.
• Analysis of live birth rates, pregnancy rates, implantation rates, and miscarriage rates.

Main Results:

• No significant difference in live birth rates for fresh embryo transfers between day 3 and day 5 biopsies.
• Significantly higher live birth rates observed with day 5 biopsy for frozen-thawed embryo transfers (P=0.0001).
• Similar rates of useful embryos and no statistical difference in unnecessarily biopsied embryos between groups.

Conclusions:

• Results support day 5 biopsy as a potential international standard due to improved frozen-thawed transfer outcomes.
• Organizational, financial, and logistical challenges currently prevent its systematic implementation in the center.