Overview

OHSS occurs when the ovaries respond excessively to IVF stimulation hormones, causing them to enlarge and release chemicals that increase vascular permeability — leading to fluid leaking into the abdomen and, in severe cases, the chest. Mild OHSS is common and self-limiting; severe OHSS is rare but requires prompt management.

Symptoms

• Mild — abdominal bloating, mild discomfort, nausea, slightly enlarged ovaries
• Moderate — significant abdominal distension, vomiting, decreased urine output
• Severe — rapid weight gain (>1kg/24h), severe abdominal pain, breathing difficulty, very low urine output, blood clot risk

Seek immediate medical attention for severe symptoms.

Who Is at Risk?

• Women with PCOS — highest-risk group
• Young women with high AFC or high AMH
• Previous history of OHSS
• Lean body type
• Large number of follicles or eggs retrieved
• hCG used as trigger injection

Prevention

• GnRH antagonist protocol — allows GnRH agonist trigger, dramatically reducing risk
• Freeze-all strategy — no fresh transfer; eliminates late-onset OHSS entirely
• Individualised lower stimulation doses for high-risk patients
• Cabergoline after egg retrieval in high-risk cases

Treatment

• Mild-to-moderate — rest, fluids, paracetamol, monitoring
• Severe — hospitalisation, IV fluids, LMWH to prevent clots, paracentesis if needed
• All embryos frozen — no fresh transfer; postponed to next cycle

Starting IVF and concerned about OHSS? Book a consultation today