IVF procedure
All the patients received a standardized ovarian stimulation regimen in the PGT-A cycles according to their ovarian function. In brief, recombinant FSH was used for ovarian stimulation in gonadotropin-releasing hormone agonist, gonadotropin-releasing hormone antagonist protocols or others. Oocyte retrieval was performed 36 h after triggering with hCG.
Insemination of retrieved oocytes was done by intracytoplasmic sperm injection (ICSI). Laser-assisted breaching of the zona pellucida was performed on day 3. The embryos were assessed on day 5 and 6, and trophectoderm (TE) biopsy was performed. Biopsied TE cells were then stored at -20℃ for future whole genome amplification (WGA) and next generation sequencing (NGS). After the biopsy, blastocysts were vitrified to be replaced in the subsequent frozen-thawed embryo transfer cycle.
Only cycles where at least one euploid blastocyst was available for transfer were included in this study. In ovulatory patients, embryo transfers were timed after ultrasound confirming ovulation. Anovulatory women were managed with an artificial hormone replacement regime. Pregnancy was confirmed by serum β-hCG assessment 14 days after embryo transfer.