OHSS Risk Score Calculator

Ovarian hyperstimulation syndrome (OHSS) is the most significant complication of controlled ovarian stimulation in IVF. Mild OHSS is common (about 20-30% of cycles) and self-limited. Moderate-to-severe OHSS (about 1-3% of cycles) involves substantial ovarian enlargement, fluid shifts, electrolyte abnormalities, and rarely thromboembolic or respiratory complications. Identifying high-risk patients before stimulation allows protocol adjustments — lower starting doses, antagonist protocols, GnRH agonist trigger instead of hCG, or freeze-all strategies — that reduce the risk substantially.

This calculator combines the most consistently reported predictors from reproductive medicine literature into a simple additive score.

Risk factors and weights:

Age under 30: +2 (younger patients have higher ovarian responsiveness) Age 30-34: +1 Age 35 or older: 0

BMI under 25: +1 (lean patients metabolize stimulation drugs differently)

PCOS diagnosis: +2 (the strongest single demographic predictor)

AMH > 3.5 ng/mL: +2 AMH 2.0-3.5 ng/mL: +1

Antral follicle count > 20: +2 AFC 12-20: +1

Previous OHSS: +2 (recurrence risk is real even with protocol changes)

Peak estradiol > 3500 pg/mL on day of trigger: +2 (cycle-specific marker) Peak estradiol 2500-3500 pg/mL: +1

Mature follicles (>= 14 mm) > 18 on day of trigger: +2 14-18 follicles: +1

Score interpretation:

0-2 points: Low risk, standard stimulation protocol acceptable. 3-5 points: Moderate risk, consider antagonist protocol, lower stimulation doses, monitor closely for fluid shifts. 6-9 points: High risk, strongly consider GnRH agonist trigger, freeze-all approach, dopamine agonist (cabergoline) prophylaxis. 10+ points: Very high risk — freeze-all is generally indicated; cycle cancellation or coasting may be discussed.

This is an educational composite score, not a validated single-tool prediction model. Real-world risk assessment in fertility clinics also weighs the patient’s protocol history, response to prior cycles, lab kinetics during stimulation, and the clinician’s experience with the specific patient. The most important risk reduction strategy in modern IVF is the freeze-all approach in high-risk patients, which essentially eliminates severe late-onset OHSS by avoiding the pregnancy-driven hCG surge.