Inclusion Criteria:

• Spontaneous menstrual cycles (21-35 days)
• Poor ovarian response per Bologna criteria (≥2 of 3): advanced age ≥40 or risk factor for POR; previous poor response (≤3 oocytes with conventional stimulation); abnormal ovarian reserve (AFC <7 or AMH <1.1 ng/mL)
• POSEIDON group recorded at enrollment (1-4) for stratified randomization and pre-specified subgroup description - corrects a known limitation of Bologna-only classification, which pools biologically distinct POR phenotypes
• Indication for IVF/ICSI
• Willing and able to undergo mandatory freeze-all/FET protocol
• Signed informed consent, including explicit acknowledgment that fresh transfer is not offered in either study arm

Exclusion Criteria:

• Contraindication to ovarian stimulation
• Known müllerian anomaly
• Uncontrolled systemic disease
• 5 prior failed IVF attempts
• Known contraindication to drospirenone (per product labeling, e.g., renal impairment, adrenal insufficiency, conditions predisposing to hyperkalemia)