Know about OHSS risk

Ovarian Hyperstimulation Syndrome (OHSS) is an uncommon, but potentially serious complication of fertility treatment, particularly of IVF / ovarian stimulation with gonadotropins – because of the type and doses of hormones used.

In short, any woman undergoing controlled ovarian stimulation with gonadotropins can develop OHSS and so should be thoroughly informed – but it certainly does not happen to all women after retrieval.

Your clinic should inform you of OHSS before your egg retrieval, some will also hand out pamphlets explaining OHSS and how they measure your own risk.

Always feel free and unbothered to ask your clinic what their guidelines are, and whether you are at risk: it is very important for you to understand your risks prior to any procedure.

In essence, because of some of the shots you're giving yourself during stims, your vascular system is made more "permeable" (meaning, fluids can move across membranes they do not normally cross).

This can lead to a fluid shift from blood vessels (where fluids normally are) into spaces where they are not normally found (like the abdomen and chest).

OHSS can range from mild, moderate, severe, to critical – the level being based on the severity of symptoms and laboratory findings. Symptoms range greatly from the more common mild bloating, to much rarer life-threatening complications (see below for symptoms).

Mild OHSS is common (estimated 20-33% of ovarian stim cycles) and usually gets better with time – and precautions such as those referenced in "How to prepare for egg retrieval?".

More severe cases require specialist care, and sometimes hospital admission for critical ones. It is estimated that moderate-to-severe OHSS occurs in ONLY approximately 1–5% of IVF cycles.

Sadly, it isn't as simple as taking a pregnancy urine test. Like the rest of ovarian stims and IVF, anticipating OHSS is not an exact science, and fertility clinics consider an array of several risk factors when assessing a woman's likelihood of developing OHSS, before retrieval, to take all necessary precautions.

These risk factors are used to customize your stims protocols adjust medication dosages, and determine preventive strategies.

Risk factors commonly monitored include the below, each being given a "rating" by the clinic staff depending on each individual case:

• Women with PCOS¹, as they have high antral follicle counts (AFC²) and often hypersensitive ovaries. They are among the highest risk group for OHSS.
• Previous OHSS in prior cycles
• High AMH³ above a certain level, considered a strong predictor of OHSS risk, as it often correlates with high ovarian reserve and follicle responsiveness.
  • US and EU guidelines consider an AMH over 3.4 ng/mL as a risk factor
• Large number of follicles: depending on the clinics, having more than a given number of follicles can signal risk. Each clinic has their own thresholds, also interpreted in combination with other factors. Some clinics may use antral follicle count (AFC), some will use the number of follicles above a given size or those retrieved
  • US and EU guidelines consider an AFC of 20-25+, or 15-20 large follicles at trigger, or 15+ eggs retrieved
• High estradiol (E2) levels during stimulation:
  • In the US, an E2 > 3,500 pg/mL on trigger day increases OHSS risk, while in the EU it is an E2 over 2,500–3,000 pg/mL
• Younger age: younger women (<30–35 years) often have higher ovarian responsiveness to stimulation, which means higher risk. OHSS risk therefore decreases with age as ovarian reserve declines, but age is by no means the determining factor.
• Use of hCG for trigger shot: hCG⁴ increases the production of what is called "VEGF" which is known to drive OHSS (VEGF = vascular endothelial growth factor – a complicated name for a key protein that plays a central role in the development and severity of OHSS).
• Other factors that can be considered by your clinic:
  • Rapidly rising estrogen levels (not just high levels)
  • High sensitivity to gonadotropins in past stimulations
  • Low body weight or low BMI: lean women may have higher serum E2 concentrations per follicle, possibly increasing vascular sensitivity
  • High peak progesterone levels
  • Early pregnancy after stimulation: if conception occurs in the same cycle, endogenous hCG from the embryo can exacerbate or prolong OHSS

The above factors are not an exhaustive list or certain diagnosis tool. Each fertility clinic has their own policies and rules, risk factors and thresholds to monitor and assess OHSS risk, based on guidelines issued by their medical associations and such.

Your fertility clinic, at each step of your IVF journey, follows a number of precautions that can contribute to minimizing OHSS risk. You can also do a number of things around/after retrieval to minimize it as well. Keep in mind that any medical treatment or procedure entails some risk.

Always ask your clinic whether you are at risk, and what they recommend you to do: they are in charge of your health and know you best!

• During ovarian stims (before the Trigger Shot), your clinic will:
  • Do frequent monitoring of estrogen levels and follicle count/size
  • Use the lowest effective doses of gonadotropins
  • Adjust your protocol as needed (for instance, in the EU, some may consider "coasting", meaning pause meds if E2 rises too fast; in the US, it is not recommended as primary strategy)
  • Some medication can be prescribed by your doctor: Cabergoline is often given with OHSS risk, but others may also be given depending on your situation

• Trigger Shot: if you are at risk, your doctor may adjust your trigger shot accordingly
  • If your protocol allows it, using a "GnRH agonist" trigger instead of hCG is an option (e.g., Lupron or Decapeptyl)
  • If hCG trigger is necessary:
    • Your doctor may use a low-dose hCG (e.g., 5,000 IU or 3,300 IU instead of the standard 10,000 IU)
    • Your doctor may do a "dual trigger" and combine a GnRH agonist trigger (Lupron) and lower dose hCG

• Post-Retrieval: you can do a number of things that can help you recover better and minimize OHSS.
  • Follow the recommendations under "What should I expect after procedure?" of our chapter How to prepare for egg retrieval?
  • Track your symptoms
  • Monitor your fluid intake and output (reduced urination despite good hydration could be a sign of OHSS).
  • Contact your clinic or go to the ER if you experience any symptom that is becoming unmanageable or too severe
    • Some ER staff may not be fully knowledgeable about egg retrieval and OHSS: explain you just had an egg retrieval surgery, and are having OHSS symptoms and need medical attention
    • Beyond the above physical symptoms, doctors have a range of things they can test for, if you are indeed experiencing OHSS that calls for medical attention.

OHSS syndrome generally includes an array of symptoms, which together form a more or less clear indication of OHSS. Those symptoms include:

• Severe bloating or abdominal distention
• Nausea/vomiting that prevents eating/drinking
• Decreased urination
• Difficulty breathing or chest tightness (dyspnea)
• Rapid weight gain (, 2+lbs per day, 5lbs in 2 days)
• Severe pelvic pain

• Myth 1: "You can't get OHSS if you're doing a freeze-all cycle."

Truth: freezing all embryos and not doing a fresh transfer greatly reduces the risk of OHSS, but it doesn't eliminate it entirely. OHSS is triggered by high hormone levels – especially hCG (human chorionic gonadotropin). Some people develop OHSS after the trigger shot or even spontaneously. Additionally, if you're already borderline OHSS when retrieving eggs, the condition can worsen in the days following.

• Myth 2: "Using a Lupron trigger means you're 100% safe from OHSS."

Truth: Lupron (GnRH agonist) triggers are often used in high-risk patients to reduce OHSS risk, and they are usually effective. However, some people still develop mild to moderate OHSS afterward, especially if they have very high estrogen levels or a large number of follicles. Rarely, severe OHSS can still occur even with a Lupron trigger.

• Myth 3: "Only people with PCOS get OHSS."

Truth: While PCOS does increase the risk, anyone can develop OHSS if their ovaries respond strongly to stimulation. Some people with no PCOS and normal hormone profiles still get it.

• Myth 4: "If I feel okay the day after retrieval, I'm in the clear."

Truth: OHSS symptoms often worsen 3–10 days after retrieval, especially if pregnancy occurs (since your body produces hCG naturally). Just because you feel fine early on doesn't guarantee it won't develop or flare up later.

• Myth 5: "You should avoid salt to reduce bloating and OHSS risk."

Truth: actually, sodium is beneficial in managing OHSS. The problem isn't salt, but fluid imbalance: sodium helps you retain fluid in your blood vessels, where it belongs, rather than leaking into your abdomen. Electrolyte-rich drinks and broths are commonly recommended during recovery for this reason.

• Myth 6: "If you get OHSS once, you'll always get it in future cycles."

Truth: having OHSS once does increase your risk, but it doesn't guarantee recurrence. Many people avoid it in future cycles by adjusting protocols: lower gonadotropin doses, using antagonist protocols, Lupron triggers, and/or freezing all embryos.