Comprehensive IVF Oocyte Retrieval and Embryo Culture

The COH protocols included the antagonist protocol, long agonist protocol, mild stimulation protocol, progestin-primed ovarian stimulation (PPOS), and ultra-long agonist protocol [17 (link)]. Recombinant human chorionic gonadotropin (r-hCG) (Merck Serono, Germany), triptorelin (Ferring, Germany), or a combination of both r-hCG and triptorelin was used for triggering to promote oocyte maturation when the diameters of at least two dominant follicles reached 18 mm. Oocytes were retrieved 36 to 38 h thereafter. IVF or ICSI was performed 39 to 40 h after ovulation induction, and the pronuclear (PN) check for fertilization was performed 16 to 18 h later. The culture medium used in the study were G-IVF (Vitrolife Sweden AB, Sweden), G-1 (Vitrolife Sweden AB, Sweden), and G-2 (Vitrolife Sweden AB, Sweden). The incubator conditions were 6% CO₂, 5% O₂, and 89% N₂. The oocytes were placed in G-IVF for fertilization and transferred to G-1 after 16 to 18 h later. Every embryo was cultured to day 3 and scored according to ASEBIR consensus [18 (link)] by two embryologists. Grade A and grade B embryos were good-quality embryos: grade A: 7–8 symmetrical blastomeres with fragmentation ≤ 10%, no multinucleation; grade B: 7–8 symmetrical blastomeres with fragmentation > 11% and ≤ 25%, or ≥ 9 cells with symmetry and ≤ 25% fragmentation. The rest were LGCEs.