Gonadotropins for PCOS Ovulation Induction: Success vs OHSS

What Are Gonadotropin Injections, and When Does PCOS Treatment Reach Them?

Gonadotropins are injectable follicle-stimulating hormone (FSH), given as urinary-derived forms (uFSH, HMG) or as recombinant FSH (rFSH), and they work by a fundamentally different route than the oral drugs that usually come before them. Clomiphene and letrozole both work indirectly — they trick the brain into releasing more of the body’s own FSH. Gonadotropins skip that step entirely and deliver the hormone directly to the ovary, which is exactly why the ovarian response is typically stronger, less predictable, and requires closer supervision than either oral option.

A 2025 Cochrane review frames gonadotropins explicitly as “a second-line treatment for ovulation induction in women with PCOS who do not ovulate or conceive after clomiphene citrate or letrozole” — the same second-line position the 2023 international evidence-based guideline assigns them. This page covers what that drug class does on its own: the success-rate and OHSS-rate evidence specific to gonadotropins, which the evidence behind letrozole overtaking clomiphene as first-line and letrozole’s own success rates cover only in passing, as one item on an escalation list.

Note: in May 2026, PCOS was renamed polyendocrine metabolic ovarian syndrome, or PMOS, by a global consensus of more than 50 organisations. Same condition, same drugs, same evidence — only the label changed. This article uses PCOS, since that is still the term most readers search.

How Well Do Gonadotropin Injections Work for PCOS?

Switching to gonadotropins probably produces more live births than continuing clomiphene, in the single largest trial available: a randomized comparison of 661 women with confirmed clomiphene failure, pooled in a 2025 Cochrane review of 15 trials and 2,348 women. That trial found a relative risk of 1.24 (95% CI 1.05–1.46, moderate-certainty evidence) for live birth — meaning that if 41% of women who continued clomiphene had a live birth, the comparable estimate for gonadotropins was between 43% and 60%. Clinical pregnancy showed a similar advantage (RR 1.31, 95% CI 1.13–1.52), though the same trial found miscarriage may be higher with gonadotropins (RR 2.23, 95% CI 1.11–4.47) and found no significant difference in multiple pregnancy between the two approaches (RR 0.89, 95% CI 0.33–2.44).

A separate, older strand of evidence describes what these numbers look like in ordinary clinical practice rather than a single trial. A widely cited review of low-dose gonadotropin regimens for PCOS found they achieved a single dominant follicle — the goal of the whole approach — in roughly 70% of treated cycles, with a multiple-pregnancy rate as low as 6% and a miscarriage rate of 20–25%, the last of which the same review flagged as still relatively high, with worse outcomes specifically noted in women with obesity. And in a population narrower than either of those — women whose PCOS had specifically not responded to clomiphene — a 2026 three-arm randomized trial of 183 women found the 61 women assigned to gonadotropins reached the highest cumulative pregnancy rate of the three approaches tested, at 41% over six months, ahead of letrozole’s 32.8% and laparoscopic ovarian drilling’s 18%. Read side by side, three independently designed sources — a large head-to-head RCT, a decades-spanning body of low-dose regimen data, and a modern three-arm resistant-population trial — agree on the same direction: gonadotropins outperform continuing an oral drug that has already failed, without guaranteeing an outcome for any individual case.

Does the Type of Gonadotropin Injection Matter?

No formulation has been shown to outperform another for live birth, which the 2025 Cochrane review addressed directly by pooling every head-to-head trial between them. Recombinant FSH showed no significant advantage over urinary-derived gonadotropins for live birth (RR 1.21, 95% CI 0.83–1.78; 5 trials, 505 women; low-certainty) or for OHSS (RR 1.48, 95% CI 0.82–2.65; 10 trials, 1,565 women; very-low-certainty). Human menopausal gonadotropin (HMG) against purified urinary FSH was even less conclusive — just 2 to 3 trials and 53 to 102 women per outcome, rated very-low-certainty across the board. Given evidence this thin, the review’s own authors suggest weighing cost and convenience rather than a proven efficacy winner, which makes formulation a decision for the prescribing clinic — driven by what’s available, covered by insurance, or already stocked — not a choice with a “better” answer a reader needs to seek out.

What Is OHSS, and How Would You Know If It Was Happening?

Ovarian hyperstimulation syndrome is what happens when the ovaries respond to stimulation with far more developing follicles than intended, releasing substances that make blood vessels leak fluid out of circulation and into the abdomen — and in more severe cases, the chest. A 2015 review that catalogued OHSS staging and prediction methods found the two strongest predictors of a high-risk response were antral follicle count and anti-Müllerian hormone (AMH) — the exact two markers that run characteristically high in PCOS, which is precisely why PCOS is treated as the single most consistent risk factor for this complication across gonadotropin cycles generally, not just a footnote for a subset of patients.

The numbers vary enormously by population, and reading them side by side is more informative than any one of them alone. A long-standing review of ovarian stimulation broadly put severe OHSS at roughly 0.5% to 5% of cycles — a general range spanning the many different stimulation contexts it covers. Set against that: zero of the 661 women in the Cochrane-reviewed gonadotropin-vs-clomiphene trial above developed OHSS in either arm, which is a real demonstration that closely monitored treatment can keep the complication rare rather than routine. Set against that again: in the smaller 183-woman resistant-PCOS trial, the 61 women on gonadotropins had the highest OHSS incidence of the three treatments tested — higher than either letrozole or laparoscopic drilling — even though the paper didn’t report an exact percentage for that arm. A single statistic cannot capture all three of these findings at once, which is the point: population and monitoring quality both move this number substantially, and PCOS moves it upward regardless of which trial you’re reading.

What matters more than any single incidence figure is recognizing the syndrome early, because it can move from mild to serious over a matter of days. Early symptoms are easy to dismiss as ordinary premenstrual bloating: abdominal fullness or tightness, mild nausea, and gradual weight gain from fluid the body is retaining rather than storing as tissue. A 2024 ASRM guideline on preventing moderate and severe OHSS — the current US clinical standard, replacing the society’s 2016 version — exists precisely because that early picture can escalate into a genuinely dangerous one: worsening abdominal pain, especially if it becomes severe or one-sided, persistent vomiting, rapid additional weight gain, visible abdominal swelling, shortness of breath or difficulty breathing while lying flat, and a marked drop in how often or how much a person is urinating. Weight gain, breathing difficulty and reduced urine output are the fluid-shift signs that separate a merely uncomfortable cycle from one that has become a medical emergency.

Why Does Gonadotropin Therapy Require Such Close Monitoring?

Gonadotropins bypass the ovary’s own single-follicle selection mechanism, delivering FSH directly rather than nudging the brain to release more of its own — which is exactly why an unsupervised cycle carries a meaningfully higher risk of an excessive, multi-follicle response than either oral drug above. Intensive in-clinic monitoring — regular ultrasound scans to track how many follicles are developing and blood tests to track hormone levels — exists specifically to catch that response while it can still be managed, which is a materially different situation from an oral drug taken at home with an occasional check-in. This is not a self-directed treatment: the specific starting approach, how the dose is adjusted cycle to cycle, and when a cycle needs to be modified or stopped are clinical decisions made by the treating fertility team based on what that individual’s scans and blood work show, not something a general article can specify in advance for a given reader.

That intensity of monitoring is also a genuine practical barrier worth naming honestly rather than glossing over: frequent visits during a treatment cycle mean real time off work, travel, and cost on top of the medication itself, and access to a clinic capable of that level of monitoring is not universal. It’s part of why gonadotropins sit below the oral drugs on the treatment ladder rather than being offered first, even though the live-birth numbers above are competitive with, or better than, continuing an oral drug that has already failed.

Who Should Gonadotropins Not Be Used For?

Gonadotropins treat anovulation specifically, and they do nothing for a cause of infertility that isn’t ovulation-related — a blocked fallopian tube, a uterine structural issue, or a male-factor sperm problem all need their own work-up and their own treatment regardless of how well an ovulation-induction drug might otherwise be expected to perform. The baseline fertility work-up that identifies which of these factors is actually at play is standard practice before or alongside any oral or injectable ovulation-induction attempt, not a step to skip because a PCOS diagnosis is already on the chart.

Body weight changes the calculus here more than it does for the oral drugs. The same low-dose regimen review that found a 70% single-follicle rate also found women with obesity had a poorer response and a higher miscarriage rate on gonadotropin therapy specifically — a pattern worth raising directly with a fertility specialist rather than assuming gonadotropins perform identically regardless of body size. And because the drug class demands frequent monitoring visits, it suits poorly anyone without reliable access to a clinic that can deliver that level of supervision throughout an entire treatment cycle — a real-world constraint, not just a clinical one.

How Do Gonadotropins Compare With Clomiphene or Letrozole?

Gonadotropins are not usually the first medication offered — that’s letrozole’s own live-birth data making the case — and this page has deliberately not repeated the oral-drug comparison covered in depth elsewhere. What’s specific to gonadotropins is the trade-off shown squarely in the 183-woman resistant-PCOS trial above: the highest pregnancy rate of the three approaches tested, alongside the highest multiple-pregnancy and OHSS risk of the three. The four evidence-backed options after clomiphene resistance — and how a specialist actually weighs that trade-off — get the fuller comparison, covering gonadotropins alongside drug-switching, combination therapy, and laparoscopic ovarian drilling without repeating the option-level detail already established on this page.

When Should You See a Fertility Specialist About This?

Gonadotropin therapy is not a treatment a reader arranges independently — it’s prescribed and monitored by a fertility specialist after oral ovulation-induction options have had a fair, monitored trial, per the 2023 international guideline. The full PCOS referral timelines — including why an irregular or absent cycle pattern usually means seeing a specialist sooner than the standard wait — apply just as much to a conversation about gonadotropins as they do to a first fertility appointment, and this page sits inside the site’s broader fertility treatment coverage rather than standing alone as a complete plan.