The most reliable SART metric is live births per intended egg retrieval — not per transfer, which inflates success numbers by excluding failed cycles. Clinics can game their rates through patient selection, multi-embryo transfers, and selective emphasis. Compare clinics within your age group, check sample sizes, and ask about metrics SART doesn't report (blastocyst conversion, freeze/thaw survival).
Key Takeaways
Live births per intended egg retrieval is the only metric that doesn't exclude patients who failed before transfer — always use this for comparisons
Per-transfer rates inflate success by excluding cancelled cycles, failed fertilization, and patients with no transferable embryos
Clinics with unusually high success rates may be turning away difficult cases or using multi-embryo transfers — investigate before assuming they're 'better'
SART data doesn't capture patient experience, lab quality specifics, pricing, or your individual prognosis — it's one input, not the whole picture
Why Clinic Success Rates Are Confusing (By Design)
SART (Society for Assisted Reproductive Technology) publishes IVF success rate data for member clinics — and most patients look at these numbers at some point. The problem: the data is genuinely useful but easy to misinterpret, and some clinics exploit this ambiguity in their marketing.
This guide will teach you to read SART data like a clinician, not a patient being marketed to.
The Most Important Number: Live Births Per Intended Egg Retrieval
SART reports multiple outcome metrics. Here's what each means and why one matters most:
| Metric | What It Measures | Manipulation Risk | Usefulness |
|---|---|---|---|
| Live births per intended egg retrieval | Percentage of patients who start a retrieval cycle and end up with a baby | Low — hardest to game | HIGHEST — this is your best apples-to-apples metric |
| Live births per transfer | Percentage of embryo transfers resulting in a live birth | HIGH — excludes patients who never made it to transfer | Misleading — inflated by excluding failed cycles |
| Clinical pregnancy rate per transfer | Percentage of transfers resulting in a detectable pregnancy | HIGH — includes pregnancies that don't reach viability | Low — pregnancies ≠ babies |
| Live births per patient (cumulative) | Total live births across all cycles for patients who started treatment | Moderate — depends on how many cycles patients do | Useful for long-term planning, less so for per-cycle decisions |
💡 Always look at live births per intended egg retrieval. A clinic boasting '60% pregnancy rate per transfer' may sound amazing, but if only 50% of patients make it to transfer, the effective rate per retrieval attempt is much lower.
How Clinics Game Their Numbers
This isn't about fraud — it's about selective emphasis and patient selection practices that make numbers look better than they are:
Patient Selection
- Turning away difficult cases: Some clinics refuse patients with very low AMH, high BMI, or advanced age — which improves their published success rates. If a clinic seems too good to be true, check whether they accept challenging patients.
- Recommending donor eggs to borderline patients: Donor egg cycles have much higher success rates. Steering patients toward donors (rather than attempting own-egg cycles) inflates overall numbers.
Reporting Practices
- Emphasizing per-transfer rates: Marketing materials highlight the highest number. Per-transfer rates exclude every patient who didn't make it to transfer (cancelled cycles, failed fertilization, no blastocysts).
- Multi-embryo transfer rates: Transferring 2–3 embryos boosts per-transfer pregnancy rates but increases twin/triplet risk. A clinic with 65% per-transfer rate using multi-embryo transfer isn't necessarily better than one with 50% using single embryo transfer.
- Cycle cancellation rates: Cancelling cycles before retrieval (when monitoring suggests poor response) removes potential failures from the denominator. Some cancellation is appropriate medicine; excessive cancellation is data management.
A 2023 analysis in Fertility and Sterility found that when adjusted for patient mix, age, and transfer practices, the actual performance gap between most SART clinics was smaller than published rates suggested. Patient selection and reporting emphasis accounted for a substantial portion of apparent clinic differences.
How to Read SART Data: Step by Step
Go to sart.org/patients/a-patients-guide-to-assisted-reproductive-technology/ and:
- Select your age group — data is broken down by <35, 35–37, 38–40, 41–42, >42
- Look at "live births per intended egg retrieval" — this is your primary comparison metric
- Check number of cycles reported — small sample sizes (<50 cycles in your age group) make statistics unreliable. Prefer clinics with larger volumes for more meaningful data.
- Compare single vs. multi-embryo transfer rates — high SET rates with good outcomes indicate better lab quality and clinical confidence
- Look at the cancellation rate — very low cancellation might mean the clinic starts cycles it shouldn't; very high might mean data management
- Check the freeze-all rate — high freeze-all rates are normal in modern practice; they don't indicate a problem
What SART Data Can't Tell You
- Your individual prognosis: Population averages don't account for your specific diagnosis, ovarian reserve, sperm parameters, or prior treatment history
- Patient experience: Communication quality, emotional support, wait times, accessibility — none of this appears in SART data
- Lab quality specifics: Blastocyst conversion rates, freeze/thaw survival rates, and ICSI fertilization rates are critical quality metrics not in SART reports. Ask clinics directly.
- Financial practices: Pricing transparency, refund programs, insurance billing — unrelated to success rates
- Why a clinic's rates changed: Year-over-year fluctuations may reflect staffing changes, lab upgrades, or simply statistical variation
National IVF Averages for Context (2024 SART Data)
| Age Group | Live Birth Per Retrieval (own eggs) | Avg Eggs Retrieved | Single Embryo Transfer Rate |
|---|---|---|---|
| <35 | 45–55% | 12–18 | 85–95% |
| 35–37 | 35–42% | 8–14 | 80–90% |
| 38–40 | 22–30% | 6–11 | 70–85% |
| 41–42 | 10–18% | 4–8 | 60–75% |
| >42 | 3–10% | 2–5 | 50–65% |
📊 Clinics reporting significantly above these averages deserve scrutiny — check their patient selection practices and transfer policies. Clinics significantly below may have valid explanations (taking harder cases, new lab, transition period) or may have quality issues worth investigating.
For red flags when evaluating clinics beyond the data, see Fertility Clinic Red Flags. For the emotional side of clinic shopping, FertileStart has validation-first resources.