What is OHSS?
💡 OHSS is ovarian hyperstimulation syndrome — a complication of IVF stimulation where ovaries enlarge excessively and fluid leaks into the abdomen and chest. Severity: mild (most cases), moderate, or severe (0.5–2%). Triggered by hCG. Risk is highest in PCOS, high responders (AMH >3.0 ng/mL, AFC >20).
OHSS (ovarian hyperstimulation syndrome) is a complication of IVF ovarian stimulation in which the ovaries respond excessively to gonadotropin medications, causing them to enlarge and leak fluid into the abdomen and chest. It ranges from mild bloating to a life-threatening condition requiring hospitalisation.
🇮🇳 India Context: OHSS is widely assessed and treated across major Indian fertility centres including Chennai, Mumbai, Bangalore, Delhi, and Hyderabad.
What are the key characteristics of OHSS?
- Caused by excessive follicular response to gonadotropins — particularly in PCOS and high ovarian responders
- Pathophysiology: hCG triggers VEGF release from granulosa cells, causing increased vascular permeability and fluid shifts
- Severity: mild (bloating, mild discomfort), moderate (ultrasound ascites, nausea/vomiting), severe (large ascites, haemoconcentration, DVT risk)
- Incidence: mild OHSS ~30%, moderate ~3–8%, severe ~0.5–2% of all stimulated IVF cycles
- Risk factors: PCOS, AMH >3.0 ng/mL, AFC >20, age <35, low BMI, prior OHSS history
- Early OHSS: within 3–9 days of trigger; late OHSS: Day 9–17 post-trigger (driven by hCG from early pregnancy)
- Freeze-all strategy eliminates late OHSS — transferring embryos in a subsequent cycle after full ovarian recovery
- Severe OHSS requires hospitalisation: IV fluids, albumin infusion, anticoagulation (DVT prophylaxis), monitoring
How does OHSS work?
Why does OHSS matter in fertility?
OHSS does not affect egg or embryo quality — but severe OHSS forces cycle cancellation or freeze-all strategy, delaying embryo transfer by one cycle. A freeze-all approach in high-risk patients reduces severe OHSS to near zero by eliminating endogenous hCG from early pregnancy — the main driver of late OHSS. OHSS-related DVT is a potentially fatal complication requiring mandatory anticoagulation. In India, baseline OHSS risk assessment (AFC, AMH, PCOS status) is standard before commencing IVF stimulation at all accredited centres.
What are related terms to OHSS?
FAQs about OHSS
What are the symptoms of OHSS?
Mild: abdominal bloating, mild pelvic discomfort, slight nausea. Moderate: significant bloating, nausea/vomiting, visible abdominal distension, confirmed ascites on ultrasound. Severe: large ascites, reduced urine output, shortness of breath, rapid weight gain (>1kg/day), clot risk.
Who is at highest risk of OHSS?
Highest risk: women with PCOS, AMH >3.0 ng/mL, AFC >20 follicles, age <35, low BMI, or prior OHSS. Egg donor cycles carry elevated OHSS risk. These patients should use low-dose stimulation and be considered for GnRH agonist trigger + freeze-all.
What is the difference between early and late OHSS?
Early OHSS occurs 3–9 days after the trigger injection — caused by exogenous hCG from the trigger. Late OHSS occurs 9–17 days post-trigger — driven by endogenous hCG from early pregnancy implantation. Late OHSS is more severe and prolonged. Freeze-all eliminates late OHSS.
Does OHSS affect egg or embryo quality?
No. OHSS does not impair egg quality or embryo development — the eggs retrieved are unaffected. However, severe OHSS may require delaying embryo transfer to allow recovery. A freeze-all strategy preserves all embryos for transfer once the patient has fully recovered.
How is OHSS treated?
Mild/moderate: rest, high fluid intake, pain relief, monitoring. Severe: hospitalisation — IV fluids, IV albumin, anticoagulation (DVT prevention), drainage of ascites if necessary, close monitoring of urine output and haematocrit. Resolution occurs in 1–6 weeks depending on severity.
Can OHSS be prevented?
Yes. OHSS can be largely prevented in high-risk patients using: low-dose stimulation, close monitoring, GnRH agonist trigger instead of hCG, freeze-all strategy, and cabergoline (dopamine agonist). With this combined approach, severe OHSS can be reduced to near zero.
📚 Learn More
🏥 Find Specialists for OHSS in India
Connect with verified fertility specialists who can guide you through ohss.