Evaluate the Effectiveness of Progestin-Primed Versus GnRH Antagonist Protocols in Vietnamese Women Undergoing In-vitro Fertilization

"Ovarian Stimulation Process:~* Stimulate ovaries with FSH \& hMG (150-375 IU) starting day 2-3 of menstruation.~* Monitor response with ultrasound \& hormones (E2, LH, P4).~* GnRH-ant arm: Prevent LH surge with Cetrorelix (0.25mg) starting day 5.~* PPOS arm: Suppress LH with Dydrogesterone (10mg x 3/day) from day 1.~* Trigger ovulation when ≥2 follicles \>17mm (Triptorelin, hCG, or rhCG).~* Oocyte retrieval 36-38 hours later (\>10mm follicles aspirated).~Embryo Culture \& Monitoring:~* Fertilize with ICSI.~* Culture \& evaluate embryos (43-45 hours, day 3/5).~* Freeze all embryos."