The Outcomes of Day 5 versus Day 3 Embryo Biopsy for Preimplantation Genetic Testing for Monogenic Diseases (PGT-M)

Objective:
Cleavage stage biopsy is still the frequently used method for PGT-M. However, blastocyst biopsy is rising due to the assumed detrimental effect of blastomere biopsy on the embryo implantation potential. To date, insufficient powered studies exist, comparing the impact of the biopsy at different stages on the reproductive outcomes. Hence, we aimed to compare the PGT-M cycle outcomes of D5 versus D3 biopsy.

Material and Methods:
A retrospective cohort study including all PGT-M cycles performed between 2019-2021 with at least eight high quality embryos suitable for biopsy on Day-3. The day of the biopsy was determined according to physician`s discretion and patient`s desire. The primary outcomes included the number of unaffected embryos per ovum pick up (OPU), implantation rate (IR), clinical pregnancy rate (CPR) and cumulative pregnancy rate per OPU.

Results:
A total of 189 cycles were included, 123 and 66 in D5 and D3 groups, respectively. The mean maternal age was 31.7 and 32.2, respectively (p=0.5). While a significantly increased number of oocytes retrieved and fertilized (2PN) were observed in D5 compared to D3 group (22.4 vs 18.4, p< 0.01; 14.4 vs 12.0, p=0.02; respectively), the number of embryos for biopsy was significantly lower in D5 versus D3 (7.1 vs. 9.1, p<0.01), resulting in non-significant difference in the number of unaffected embryos (2.4 vs. 2.8, p=0.2; respectively). 1 and 1.1 embryos were transferred in the D5 and D3 groups yielding no significant differences in IR (29.5 vs 31.6, p=0.8), CPR (25.2 vs 37.9, p=0.08) and cumulative PR (36.0 vs 40.3, p=0.6) per OPU, respectively.

Conclusion:
Blastocyst stage biopsy doesn`t improve the clinical outcomes of PGT-M cycles.