Polycystic ovary syndrome (PCOS) is a common cause of irregular ovulation, and many women with PCOS conceive with ovulation-inducing medication alone. Some, however, go on to need in vitro fertilisation (IVF), either because simpler treatments have not worked or because another factor, such as blocked fallopian tubes, a significant male factor or advancing age, makes IVF the more suitable route. Women with PCOS often respond very strongly to ovarian stimulation, so IVF planning focuses on two goals at once: collecting a useful number of eggs, and avoiding an excessive response that could lead to ovarian hyperstimulation syndrome (OHSS).This article explains why PCOS changes IVF planning, the main strategies used to lower OHSS risk, and what the evidence does and does not show. It is general education and not individual medical advice.

When is IVF considered in PCOS?

The 2023 International Evidence-based Guideline for PCOS describes a stepped approach to infertility. Letrozole is the first-line drug treatment for ovulation induction; clomiphene (alone or with metformin), injectable gonadotrophins or laparoscopic ovarian surgery are second-line options; and IVF, which may include in vitro maturation (IVM) in some settings, is positioned as third-line treatment when ovulation induction has not succeeded and there is no absolute indication for IVF. An "absolute indication" means a situation where IVF is needed from the start, for example severe tubal disease or a severe male factor.The right timing therefore depends on age, how long the couple has been trying, response to earlier treatment, and whether other fertility factors are present. In women of older reproductive age, clinicians may move to IVF sooner because time is a limiting factor.

Why PCOS changes the IVF plan

PCOS ovaries typically contain a large number of small, antral follicles. When gonadotrophin injections are used, many of these follicles can respond at once. This can be helpful, since more eggs may be collected, but it also raises the risk of a very high oestrogen level, enlarged ovaries and OHSS.OHSS is a condition in which the ovaries overreact to fertility drugs and fluid shifts from the bloodstream into the abdomen and sometimes the chest. Most cases are mild and settle on their own, with symptoms such as bloating and abdominal discomfort. A small number become moderate or severe, with rapid weight gain, marked abdominal swelling, vomiting, reduced urine output or breathlessness, which need urgent medical assessment and sometimes hospital care. OHSS can occur early, within days of the trigger injection, or late, in association with an early pregnancy because pregnancy hormones prolong the stimulation of the ovaries.

Strategies used to lower OHSS risk

No single measure removes every risk, so clinics usually combine several. The main strategies, as described in the European Society of Human Reproduction and Embryology (ESHRE) ovarian stimulation guideline, are summarised below. The 2019 guideline has since been updated; the 2025 update (published 2026) was developed from evidence available to February 2025 and includes dedicated recommendations on preventing OHSS. Its authors also note that most recommendations rest on low or very low quality evidence, which is a reminder that individual decisions rely on clinical judgement as well as trial data.

1. Careful stimulation dosing

Stimulation is individualised using age, ovarian reserve tests such as antral follicle count or anti-Müllerian hormone (AMH), body weight and previous response. In women predicted to be high responders, doses are generally chosen conservatively, and the response is followed with blood tests and serial ultrasound scans so the plan can be adjusted if the follicle count rises quickly.

2. The GnRH antagonist protocol

Stimulation cycles differ in how they prevent a premature natural LH surge. In the GnRH antagonist protocol, an antagonist medicine is added part-way through stimulation to block the surge. The 2019 ESHRE guideline made a strong recommendation that the GnRH antagonist protocol be used in women with PCOS, because it improves safety by reducing OHSS risk while achieving comparable effectiveness.

3. Choice of trigger

The trigger injection is the final step that matures the eggs before collection. The traditional trigger uses hCG, a hormone that stays active in the body for several days and can intensify OHSS. In an antagonist cycle, a GnRH agonist can be used instead. It causes a shorter surge of the body's own LH and FSH, and the ESHRE guideline strongly recommends a GnRH agonist trigger for women at risk of OHSS because it substantially lowers the risk of early-onset OHSS. The trade-off is that live birth rates after fresh embryo transfer following an agonist trigger have been reported to be lower, which is why this approach is often paired with freezing embryos.

4. A freeze-all strategy

In a freeze-all approach, embryos are cryopreserved and transferred in a later cycle rather than in the stimulation cycle. The ESHRE guideline strongly recommends freeze-all to fully eliminate the risk of late-onset OHSS, since there is no early pregnancy hormone rise during the same cycle, although it advises that women should still be followed up. Late-onset OHSS is the form linked to a pregnancy that begins in the same cycle.The evidence for frozen transfer in PCOS comes from a large randomised trial in China published in the New England Journal of Medicine in 2016. Among women with PCOS undergoing their first IVF cycle, live birth after the first transfer was 49.3% with frozen embryo transfer and 42.0% with fresh transfer. OHSS occurred in 1.3% of the frozen group and 7.1% of the fresh group, and pregnancy loss was lower with frozen transfer (22.0% versus 32.7%). However, the frozen group had a higher rate of pre-eclampsia (4.4% versus 1.4%). Frozen transfer is therefore widely considered a reasonable option in PCOS, but it is a decision to be individualised, and the trial reflects a particular population and set of clinic practices.

5. Medicines that are not routinely recommended

Some adjunct medicines have been studied for OHSS prevention. For women with PCOS using an antagonist protocol, the 2019 ESHRE guideline recommended against routine use of adjuvant metformin during stimulation because it did not reduce OHSS in that setting. It also advised against adding cabergoline or albumin as additional preventive measures when a GnRH agonist trigger is used. These conclusions illustrate that preventive strategies should be chosen on the basis of evidence, not simply because they are available.

Egg quality, numbers and embryo transfer in PCOS

Women with PCOS often produce many eggs, but a higher egg count does not automatically mean a higher chance of a healthy pregnancy per egg, and the aim is a safe and effective number rather than the largest possible number. When embryos are available, transferring a single embryo is generally preferred to reduce the risk of multiple pregnancy, which carries additional risks for both mother and babies. Decisions about how many embryos to transfer, and whether to culture them to the blastocyst stage, depend on age, embryo quality and previous outcomes.

In vitro maturation (IVM)

IVM involves collecting immature eggs and maturing them in the laboratory, and it can be performed with little or no ovarian stimulation. The 2023 guideline summary mentions IVM as a possible option within IVF in PCOS. It is not available everywhere and is less widely used than conventional IVF.

Health before and during treatment

PCOS is associated with metabolic differences, including insulin resistance, and with a higher risk of pregnancy complications such as gestational diabetes and hypertensive disorders. The 2023 guideline recommends that blood pressure be measured when planning pregnancy or seeking fertility treatment, and that an oral glucose tolerance test be considered in women without pre-existing diabetes who are planning pregnancy. It also advises counselling about how weight can affect treatment outcomes while avoiding weight stigma, and optimising factors such as smoking, alcohol, diet, folate intake, exercise and sleep before conception.

Recognising OHSS and when to seek care

Women undergoing IVF are usually told which symptoms to watch for in the days after egg collection. Mild bloating is common. Care should be sought promptly if there is rapid weight gain, increasing abdominal swelling or pain, persistent vomiting, passing very little urine, shortness of breath, or severe dizziness. Prompt assessment allows fluid balance, blood tests and scans to be reviewed, and most women recover fully with appropriate care.

Questions worth asking your fertility team

  • Is IVF the right next step for me, or should ovulation induction be tried or continued first?
  • Which stimulation protocol and trigger will be used, and why?
  • Is a freeze-all approach being proposed, and what are the benefits and limitations in my case?
  • How will my response be monitored, and what would trigger a change of plan?
  • How many embryos would be transferred, and what are the risks of multiple pregnancy?
  • Which symptoms after egg collection should prompt an urgent call?

Key takeaways

PCOS does not prevent successful IVF, but it changes how treatment is planned. Individualised dosing, an antagonist protocol, a GnRH agonist trigger when appropriate and a freeze-all strategy are the main tools used to lower the risk of OHSS, with the strongest recommendations supported by guideline groups and, for freeze-all, a large randomised trial that also showed a signal of higher pre-eclampsia that deserves consideration. Evidence quality across many stimulation decisions remains modest, no approach guarantees a pregnancy, and the best plan for any individual depends on age, diagnosis, ovarian response and personal circumstances.

Author

Dr. Pranay Shah, M.S. (Obstetrics & Gynaecology), is an IVF specialist and Chief Fertility Consultant at Wellspring IVF & Women’s Hospital, Ahmedabad, India. His clinical focus centers on reproductive endocrinology, patient safety in ovarian stimulation, and evidence-based assisted reproductive technologies. No relevant conflicts of interest declared beyond clinical affiliation.

References

  1. Teede HJ, Tay CT, Laven J, et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Human Reproduction. 2023;38(9):1655–1679. https://academic.oup.com/humrep/article/38/9/1655/7246644
  2. International PCOS Network (Monash University). International evidence-based guideline for the assessment and management of polycystic ovary syndrome 2023. Monash University; 2023. https://pcoschallenge.org/pdf/PCOS-Evidence-Based-Guideline.pdfESHRE 
  3. Reproductive Endocrinology Guideline Group. Ovarian stimulation for IVF/ICSI: Guideline of the European Society of Human Reproduction and Embryology. ESHRE; October 2019. https://www.ESHRE.EU/-/media/sitecore-files/Guidelines/COS/ESHRE-COS-guideline_final-09102019_.pdf
  4. ESHRE Guideline Group on Ovarian Stimulation. ESHRE guideline: ovarian stimulation for IVF/ICSI: an update in 2025. Human Reproduction. 2026;41(4):498–514. doi:10.1093/humrep/deag018. https://doi.org/10.1093/humrep/deag018
  5. Chen ZJ, Shi Y, Sun Y, et al. Fresh versus Frozen Embryos for Infertility in the Polycystic Ovary Syndrome. New England Journal of Medicine. 2016;375:523–533. https://ivf-worldwide.com/ivf-selected-publications/nejm/841-fresh-versus-frozen-embryos-for-infertility-in-the-polycystic-ovary-syndrome-aug-2016.html
  6. World Health Organization. Polycystic ovary syndrome (fact sheet). WHO; 22 January 2026. https://www.who.int/news-room/fact-sheets/detail/polycystic-ovary-syndrome