Egg retrieval is a 15-30 minute procedure under sedation, and its most serious risk — ovarian hyperstimulation syndrome (OHSS) — is now largely preventable. A GnRH agonist trigger with freeze-all cuts moderate-to-severe OHSS in high-risk patients from 5-10% to under 1%.
“Ovarian hyperstimulation syndrome (OHSS) is an exaggerated response to excess hormones.” — American Society for Reproductive Medicine, ASRM, Ovarian Hyperstimulation Syndrome patient FAQ
This guide’s evidence base is the ESHRE ovarian stimulation guideline, 2025 update, the ASRM OHSS practice guideline, Cochrane reviews, and 2024-2025 randomised trials. If you are still mapping the treatment, read the step-by-step IVF process guide first.
What Happens During Egg Retrieval?
Retrieval is scheduled 34-36 hours after the hCG or GnRH agonist trigger injection. It takes 15-30 minutes under intravenous sedation.
How should you prepare before the procedure?
- Fasting: no food for 6-8 hours and no water for 2 hours for anaesthesia safety.
- Bladder and bowel: empty your bladder — transvaginal retrieval needs no full one — and empty the rectum if told.
- Medication check: confirm your stimulation protocol and that the trigger time and dose are correct.
What happens in the procedure room?
An embryologist or physician guides a needle through the vaginal wall via a transvaginal ultrasound probe, aspirating fluid from each mature follicle.
Table 1: Key quality indicators for egg retrieval
| Indicator | Reference range | Notes |
|---|---|---|
| Procedure duration | 15-30 minutes | Depends on follicle count and ovarian position |
| Follicle recovery rate | 80-90% | Punctured follicles that yield an egg |
| Post-op observation | 1-2 hours | Discharge once vital signs are stable |
| Anaesthesia | IV sedation or general | Patient factors plus clinic protocol |
| No heavy physical activity | 2 weeks | Lowers ovarian torsion and bleeding risk |
Source: ESHRE guideline: ovarian stimulation for IVF/ICSI, 2025 update, Hum Reprod 2026
These are clinic-level quality benchmarks, not individual predictions. The Society of Assisted Reproductive Technology, SART and CDC ART success rates publish comparable US clinic-level data.
What should you do in the first 48 hours?
- Rest: avoid strenuous activity on retrieval day and take it easy for 4-6 hours.
- Eat protein: fish, eggs, lean meat and legumes support plasma oncotic pressure; drink plenty of fluids.
- Track symptoms: record daily weight, abdominal girth and urine output, and watch for worsening bloating.
- Keep taking medication: continue prescribed luteal support (progesterone) without stopping on your own.
- Attend follow-up: return on day 3-5 for the embryo report and the transfer or freeze-all decision.
The day 3-5 review is also where OHSS is first graded, so report symptom changes. For the transfer decision, see our embryo transfer aftercare guide.
Why Does OHSS Happen?
OHSS begins with hCG: human chorionic gonadotropin binds ovarian granulosa-cell receptors and drives overproduction of VEGF (vascular endothelial growth factor), which makes capillaries abnormally leaky.
The core pathway: hCG to VEGF to vascular leak
- Plasma shifts out of blood vessels into the third space — abdomen, chest, pericardium.
- Circulating volume and kidney perfusion fall, and urine output drops (oliguria).
- Blood concentrates, viscosity rises, and thrombosis risk increases.
- In severe cases: shock, renal failure, and acute respiratory distress syndrome (ARDS).
Why does IVF stimulation make you more vulnerable?
In a natural cycle only one follicle grows, so VEGF output stays low. After IVF stimulation, dozens of follicles develop at once, and the far larger granulosa mass releases exponentially more VEGF under hCG — that is what “hyperstimulation” means.
Source: Soares SR et al., Hum Reprod Update, 2008; ESHRE guideline 2025 update
Early or late OHSS: which one can you prevent?
| Type | Timing | Trigger | Key feature |
|---|---|---|---|
| Early onset | 3-7 days after retrieval | hCG trigger | Primary prevention target — a GnRH agonist trigger nearly eliminates it |
| Late onset | 10-14 days after transfer | Endogenous hCG from pregnancy | Occurs only in pregnancy and cannot be fully prevented |
Early OHSS is the priority because its trigger — the exogenous hCG injection — is the one variable your clinic controls.
How Likely Is OHSS in Your Case?
Moderate-to-severe OHSS affects roughly 3-6% and 0.1-2% of cycles overall, but personal risk depends on AMH, antral follicle count, age, BMI, PCOS and prior OHSS.
What are the four clinical grades?
Table 2: OHSS clinical grading
| Grade | Core symptoms | Incidence | Management |
|---|---|---|---|
| Mild | Bloating, mild abdominal pain, nausea | 20-33% | Outpatient observation, high-protein diet |
| Moderate | Ascites visible on ultrasound, vomiting, weight gain over 3 kg | 3-6% | Close monitoring, consider outpatient IV fluids |
| Severe | Clinical ascites, oliguria, breathing difficulty, hemoconcentration | 0.1-2% | Immediate admission, anticoagulation and volume correction |
| Critical | Renal failure, thrombosis, ARDS | Below 0.1% | ICU care |
Data: ASRM Practice Committee OHSS guideline, Fertil Steril, 2016; ESHRE guideline 2025 update
Mild symptoms are common and self-limiting; only moderate and above change your protocol.
Which risk factors put you in which tier?
Table 3: OHSS risk factor stratification
| Risk factor | Low | Moderate | High | Very high |
|---|---|---|---|---|
| AMH (ng/mL) | < 1.2 | 1.2-3.4 | 3.4-6.0 | > 6.0 |
| AFC (antral follicle count) | < 10 | 10-20 | 20-30 | > 30 |
| Age | Over 38 | 35-38 | 30-35 | Under 30 |
| BMI | > 25 kg/m² | 20-25 | 18-20 | < 18 |
| Previous OHSS | None | None | Yes (mild) | Yes (moderate-severe) |
| PCOS | No | No | Yes | PCOS plus high AMH |
Expected moderate-to-severe OHSS rates by tier: low risk under 0.5%, moderate 1-3%, high 5-10%, very high 10-20%.
Sources: ESHRE OHSS prevention guideline, Hum Reprod Open, 2019; Papanikolaou EG et al., Fertil Steril, 2006
Highest-risk profile: under 30, PCOS, and AMH above 6 ng/mL — moderate-to-severe OHSS occurs in 15-20% of these patients, and the most aggressive prevention strategy is mandatory rather than optional.
Which OHSS Prevention Protocol Works Best?
Five strategies carry real evidence and stack rather than compete: protocol choice and trigger type first, adjunct drugs second.
Table 4: OHSS prevention protocols compared
| Protocol | Core mechanism | Reduction in moderate-severe OHSS | Evidence level | Best suited to | How it is given | Relative cost |
|---|---|---|---|---|---|---|
| GnRH agonist trigger + freeze-all | Shortens gonadotropin stimulation, removes hCG, drops VEGF | 80-90% (incidence below 1%) | ★★★★★ multiple RCTs plus meta-analysis | All high-risk patients; first choice in PCOS | Single injection on trigger day | $$ |
| Cabergoline | Dopamine agonist that inhibits VEGF phosphorylation | about 50% | ★★★★★ Cochrane systematic review | Patients who cannot use a GnRH agonist trigger; as an adjunct | 0.5 mg daily for 8 days from trigger | $ |
| IV calcium gluconate | Stabilises vascular endothelium, lowers permeability | about 50% | ★★★★ multicentre RCT, 2024 | When cabergoline is contraindicated or not tolerated | IV infusion on trigger day plus 2 days | $$ |
| Hydroxychloroquine (HCQ) | Anti-inflammatory, reduces vascular exudation | 50-60% preliminary (limited data) | ★★★ small 2025 RCT | High-risk PCOS patients (emerging option) | Oral, from trigger day | $ |
| Individualised stimulation | Low-dose step-up plus antagonist protocol to control follicle number | 20-40% | ★★★★★ foundational strategy | Every patient, as baseline prevention | Throughout stimulation | — |
Is GnRH agonist trigger with freeze-all the gold standard?
Yes — it is the single most effective prevention for early OHSS. Replacing hCG with a GnRH agonist (triptorelin or leuprolide) and freezing all embryos cuts moderate-to-severe OHSS from 5-10% to under 1% in high-risk patients (ESHRE 2025 guideline, PMID 41732035; Li Y et al., Arch Gynecol Obstet, 2024, PMID 38032411).
The mechanism is duration: a GnRH agonist induces a far shorter LH peak than an hCG injection, so granulosa cells are stimulated for less time and secrete less VEGF. One limitation matters — a GnRH agonist trigger does not work after a long protocol because the pituitary is already down-regulated, so high-risk patients should start on an antagonist protocol, as explained in our stimulation protocols guide.
Does cabergoline really reduce OHSS?
Yes, by roughly half. The Cochrane review of dopamine agonists for OHSS prevention, 2016 pooled 10 RCTs and 1,009 patients, finding an OHSS risk ratio of 0.42 (95% CI 0.29-0.62) at 0.5 mg daily for 8 days from trigger.
Can IV calcium gluconate replace cabergoline?
It can, when cabergoline is contraindicated or poorly tolerated. A 2024 systematic review and meta-analysis — PMID 39084180 — found 10 mL of 10% calcium gluconate IV on trigger day plus 2 days after performed comparably to cabergoline.
Is hydroxychloroquine an option yet?
Not as standard care. A small 2025 RCT in PCOS patients — Kheirkhah A et al., J Ovarian Res, PMID 40442814 — reported a 50-60% preliminary OHSS reduction, but the sample was small and HCQ is not yet guideline-recommended.
What does individualised stimulation actually mean?
It is the baseline under every other strategy: antagonist rather than long protocol, minimum effective FSH dose, dynamic adjustment to follicle count and estradiol, and no hCG trigger when E2 exceeds 3,500 pg/mL. Those choices alone lower OHSS risk by 20-40%.
How Do You Match Prevention to Your Risk Level?
Start from Table 3, then read across the decision matrix for your tier; the inputs are AMH, AFC, age, BMI, PCOS status and prior OHSS.
Table 5: OHSS prevention decision matrix
| Risk tier | Stimulation protocol | Trigger | Adjunct drugs | Transfer strategy | Post-retrieval monitoring |
|---|---|---|---|---|---|
| Low | Antagonist or long protocol | hCG or GnRH agonist | None needed | Fresh or frozen | Routine follow-up |
| Moderate | Antagonist (preferred) | GnRH agonist (strongly recommended) | Optional cabergoline | Frozen preferred | Review at day 3 |
| High | Antagonist (mandatory) | GnRH agonist (mandatory) | Cabergoline or calcium (recommended) | Freeze-all (mandatory) | Reviews at day 3 and day 7 |
| Very high | Antagonist (mandatory) | GnRH agonist (mandatory) | Cabergoline plus consider adding calcium | Freeze-all (mandatory) | Close monitoring for 1-2 weeks |
Costs move with these choices — medication, adjuncts and freeze-all storage add line items, broken down in the IVF cost guide.
What does follow-up look like after retrieval?
- High and very high risk: return on day 3 and day 7 for haematocrit, liver and kidney function, and ultrasound assessment for ascites.
- If symptoms appear: mild OHSS is managed outpatient with high-protein diet and hydration; moderate or severe OHSS needs admission.
- If you conceive after a fresh transfer: endogenous hCG can trigger late OHSS, so monitoring continues to week 8-10 of pregnancy.
What Else Can Go Wrong After Retrieval?
Non-OHSS complications are each rarer than 1% but have distinct warning signs.
Bleeding
Intra-abdominal bleeding after transvaginal retrieval occurs in about 0.1-0.5% of cycles. Light blood-tinged discharge is normal, but seek care for bright red bleeding heavier than a period, severe abdominal pain, or falling blood pressure with dizziness and pallor.
Infection
Pelvic infection occurs in roughly 0.1-0.3% of retrievals, more common with a history of PID, hydrosalpinx or endometrioma. A 2026 study found very low infection risk after endometrioma aspiration — PMID 41643412 — yet prophylactic antibiotics remain standard practice.
Ovarian torsion
Torsion is rare, at about 0.01-0.1%, because the enlarged post-stimulation ovary can rotate on its pedicle. Sudden severe one-sided lower abdominal pain with nausea and vomiting is a surgical emergency.
Anaesthesia reactions
IV sedation is broadly safe, but some patients experience nausea, dizziness or allergic reactions. Give the anaesthesiologist your full anaesthesia and allergy history beforehand.
Which Common Beliefs About OHSS Are Wrong?
Four beliefs drive most preventable OHSS cases, each with an evidence-based correction.
Myth 1: “Only women with PCOS get OHSS”
Fact: PCOS is the highest-risk group, but any woman who stimulates can develop OHSS — around 30% of cases occur without PCOS. High AFC, AMH above 3.4 ng/mL, young age and low BMI are independent risk factors.
Myth 2: “More eggs is better, and I can just rest afterwards”
Fact: Retrieving more than 20 eggs adds no live birth benefit while sharply raising OHSS and bleeding risk. Sunkara SK et al., Hum Reprod, 2011 analysed 400,000 cycles and found cumulative live birth peaks at 8-15 eggs; beyond 20 the rate plateaus or falls as OHSS risk climbs.
Myth 3: “Freezing all embryos lowers my chances”
Fact: Large RCTs and meta-analyses show frozen embryo transfer live-birth rates are non-inferior to fresh. For high-risk patients, freeze-all also removes the high-hormone environment that may impair receptivity — see the embryo transfer aftercare guide.
Myth 4: “OHSS passes on its own if I wait”
Fact: Mild OHSS is self-limiting, but moderate and severe OHSS will not resolve without treatment. Severe cases progress to pre-renal failure, thromboembolism and ICU admission, and both ASRM and ESHRE require supervised management rather than waiting at home.
When Is It an Emergency?
Contact your clinic or go to an emergency department immediately for any of these after retrieval.
- Severe abdominal pain that does not settle or keeps worsening
- Marked bloating — visibly distended, hard abdomen with restricted breathing
- Oliguria — under 500 mL of urine in 24 hours
- Rapid weight gain — more than 1 kg in 24 hours
- Fever above 38.5 °C, suggesting infection
- Breathing difficulty — short of breath lying flat, needing to sit up
- Bright red vaginal bleeding heavier than your period
FAQ
Q: Is egg retrieval painful?
No — the procedure runs under IV sedation and takes 15-30 minutes, so you feel nothing during it. Afterwards, mild cramping lasts 1-2 days and responds to ordinary painkillers like ibuprofen.
Q: How many eggs should be retrieved for the best outcome?
The best quality-per-egg balance sits at 10-15 eggs; cumulative live birth peaks at 8-15 in Sunkara et al.’s 400,000-cycle analysis. Beyond 15-20 eggs, OHSS risk rises sharply with no further live birth gain — see the stimulation protocols guide.
Q: Can OHSS happen even with a GnRH agonist trigger?
Yes, but small: a GnRH agonist trigger plus freeze-all pushes moderate-to-severe OHSS below 1% in high-risk patients, versus 5-10% with an hCG trigger. Late OHSS from pregnancy is still possible, so monitoring continues to week 8-10 if you conceive.
Q: Does OHSS cancel my embryo transfer?
Moderate or severe OHSS means your doctor cancels the fresh transfer, freezes all embryos, and reschedules 1-3 months later once symptoms resolve; frozen cycles achieve comparable pregnancy rates.
Q: What should I eat to lower OHSS risk?
High-protein foods (fish, shrimp, eggs, lean meat, legumes) and potassium-rich foods (bananas, potatoes, tomatoes) support plasma oncotic pressure and limit fluid shift; keep salt and gas-producing items like beans and carbonated drinks low.
Diet is supportive only — mild OHSS still occurs in 20-33% of cycles whatever you eat, so pair it with the trigger and monitoring plan above.
Q: When can I resume sex after egg retrieval?
Wait until your next period ends, typically 2-4 weeks; earlier activity raises bleeding and infection risk while the ovaries are still enlarged.
Q: Do I need special preparation if I have PCOS or high AMH?
Agree the OHSS plan before you start: antagonist protocol, GnRH agonist trigger, prophylactic cabergoline or calcium; our PCOS IVF guide and IVF over 35 guide cover how these interact with age and reserve.
The Bottom Line on Egg Retrieval Safety
Egg retrieval is safe and short, and OHSS is the one complication worth planning for. Prevention works best before stimulation, not after symptoms appear.
Before your first trigger injection, four things should be settled:
- Your OHSS risk tier (AMH, AFC, age, BMI, PCOS, prior OHSS)
- Your protocol, with antagonist stimulation for anyone at high risk
- Your prevention plan, including trigger type, adjunct drugs, and whether freeze-all applies
- Your monitoring routine after retrieval — weight, abdominal girth and urine output
Run a pre-cycle review with the IVF preparation checklist, and compare clinics with published OHSS and lab data in our IVF hospital directory.
References
- ESHRE Guideline Group. Ovarian Stimulation for IVF/ICSI — 2025 Update. Human Reproduction, 2026. PMID 41732035 · DOI 10.1093/humrep/deag018
- ASRM Practice Committee. Prevention and Treatment of Moderate and Severe Ovarian Hyperstimulation Syndrome: A Guideline. Fertility and Sterility, 2016;106(7):1634-1647. PMID 27678032
- Soares SR, et al. Pathophysiology and Management of Ovarian Hyperstimulation Syndrome. Human Reproduction Update, 2008;14(4):321-333. PMID 18430766
- Mourad S, et al. Calcium versus Cabergoline for Prevention of Ovarian Hyperstimulation Syndrome: A Systematic Review and Meta-Analysis. Eur J Obstet Gynecol Reprod Biol, 2024;301:140-148. PMID 39084180
- Youssef MA, et al. Dopamine Agonists for Preventing Ovarian Hyperstimulation Syndrome. Cochrane Database of Systematic Reviews, 2016. DOI 10.1002/14651858.CD008605.pub3
- Kheirkhah A, et al. Comparative Study of Cabergoline and Hydroxychloroquine to Prevent OHSS in PCOS Patients. Journal of Ovarian Research, 2025. PMID 40442814
- Sunkara SK, et al. Association Between the Number of Eggs and Live Birth in IVF Treatment: An Analysis of 400,000 Treatment Cycles. Human Reproduction, 2011;26(6):1768-1774. DOI 10.1093/humrep/der106
- ESHRE Guideline Group on OHSS Prevention. Human Reproduction Open, 2019. DOI 10.1093/hropen/hoz008
- Papanikolaou EG, et al. Incidence and Prediction of Ovarian Hyperstimulation Syndrome in Women Undergoing GnRH Antagonist IVF Cycles. Fertility and Sterility, 2006;85(1):112-120. PMID 16412739
- Li Y, et al. Effect of GnRH Agonist Trigger with or without Low-Dose hCG on Reproductive Outcomes for PCOS Women with Freeze-All Strategy. Archives of Gynecology and Obstetrics, 2024;309(2):723-731. PMID 38032411
- CDC. Assisted Reproductive Technology Success Rates and Fertility Clinic Reports. cdc.gov/art
About this article: researched and written by the ProIVF Medical Editorial Team following Google E-E-A-T health content guidelines and reviewed by the ProIVF Medical Advisory Board. Incidence figures are population-level references, not predictions of individual outcome — confirm your personal OHSS risk with a reproductive endocrinologist.
This article is for informational purposes only and is not medical advice.
Editorial standards: ProIVF About page. Last updated: 2026-09-20.
