Disclaimer: This guide is for informational purposes only. It does not constitute medical advice. Clinic selection should involve direct consultation with a reproductive endocrinologist and a thorough evaluation of your individual needs.
Beyond Success Rates: Other Metrics That Matter
Success rates get all the attention, but they are just one dimension of clinic quality. These additional metrics — most of them publicly available — can tell you things that success rates alone cannot.
Key Takeaway
A clinic with a 45% success rate and a 90% single embryo transfer rate is genuinely excellent. A clinic with a 50% success rate and a 40% SET rate is inflating results by transferring multiple embryos — putting patients at risk of twins and triplets. Always look at the full picture.
Single Embryo Transfer (SET) Rate
This is arguably the most underappreciated quality metric in fertility medicine. The SET rate tells you what percentage of embryo transfers used a single embryo rather than multiple embryos.
Why it matters: Transferring multiple embryos inflates per-cycle success rates because the chance of at least one implanting is higher. But multiple transfers also dramatically increase the risk of twins (and triplets), which carry serious health risks:
- Preterm birth (over 50% of twins are born before 37 weeks)
- Low birth weight
- Pre-eclampsia for the mother
- Neonatal intensive care (NICU) stays averaging $76,000+ per infant
- Higher rates of long-term developmental complications
Evidence-based practice is to transfer one embryo at a time, especially for patients under 38 with good prognosis. The American Society for Reproductive Medicine (ASRM) has issued clear guidelines recommending SET for most patients.
How to read it: A SET rate above 80% is excellent. Below 50% should raise questions. A clinic with a modest success rate but very high SET rate may be providing more responsible care than a clinic with a flashy success rate built on routine double or triple transfers.
PlainFertility displays SET rates alongside success rates for every clinic — check the clinic directory to compare.
Cycle Volume
Cycle volume — the total number of IVF cycles a clinic performs per year — is a proxy for experience and statistical reliability.
Why Volume Matters for Statistics
A clinic performing 20 cycles/year with a reported 60% success rate has enormous statistical noise. If they had 12 live births out of 20 cycles, a single different outcome would change their rate by 5 percentage points. Compare this to a clinic doing 500 cycles — their rate is based on hundreds of data points and is far more reliable.
Why Volume Matters for Quality
High-volume centers typically have:
- More experienced embryologists and nurses
- More refined protocols based on larger datasets
- Better-equipped laboratories with redundant systems
- More capacity to handle complex cases
However, volume is not destiny. Smaller specialty clinics can achieve excellent results through focus and expertise. Use volume as context, not as a deciding factor.
Fresh vs. Frozen Transfer Breakdown
The ratio of fresh to frozen embryo transfers tells you about a clinic's approach to treatment. Many leading clinics have shifted to a "freeze-all" strategy — freezing all embryos and performing a frozen embryo transfer (FET) in a subsequent cycle.
Why freeze-all can be better: After ovarian stimulation, the uterine environment may not be optimal for implantation. By waiting and transferring a frozen embryo into a naturally-cycling or medically-prepared uterus, some clinics see improved implantation rates.
Modern vitrification (ultra-rapid freezing) achieves thaw survival rates above 95% at experienced labs — making frozen cycles nearly as effective as fresh in terms of embryo survival.
A clinic with a high proportion of frozen transfers is likely following current best practices. Compare both fresh and frozen success rates on the PlainFertility state pages.
Donor Egg Proportion
Clinics vary in what proportion of their cycles use donor eggs. This matters because donor egg cycles have substantially higher success rates (50–70%) regardless of the recipient's age.
A clinic that does many donor egg cycles will have a higher overall success rate even if its own-egg rates are average. When comparing clinics, always compare same-egg-type, same-age-group rates — not the headline number.
Cancellation Rate
Not every IVF cycle that starts makes it to egg retrieval. Some cycles are cancelled before retrieval due to poor ovarian response (too few follicles developing) or, less commonly, ovarian hyperstimulation risk.
Cancellation rates are not widely published but are worth asking about during consultations. A very low cancellation rate might indicate a clinic is including poor-prognosis patients in retrieval who would be better served by cancelling and adjusting protocol. A very high cancellation rate may indicate protocol issues or overly conservative decision-making.
Laboratory Metrics
The embryology laboratory is where the most consequential microscopic work happens. Key lab metrics include:
Fertilization Rate
The percentage of mature eggs that fertilize normally. With ICSI, this should be approximately 70–80%. Significantly lower rates suggest laboratory technique issues that affect overall outcomes downstream.
Blastocyst Development Rate
The percentage of fertilized eggs that develop to the blastocyst stage (day 5–6). A strong lab achieves 40–60% blastocyst rates. This metric reflects culture conditions, media quality, and embryologist expertise. Low blastocyst rates mean fewer embryos available for transfer and testing.
Freeze-Thaw Survival Rate
The percentage of frozen embryos that survive the thawing process. Modern vitrification should achieve 95%+ survival. Below 90% indicates a potential laboratory weakness that directly reduces the number of usable embryos per cycle.
Most clinics do not publish these metrics publicly, but you can and should ask during a consultation. See our clinic evaluation guide for the full list of questions.
Multiple Gestation Rate
This is the percentage of pregnancies resulting in twins or higher-order multiples. It is the flip side of the SET rate — clinics with high SET rates have low multiple gestation rates, and vice versa.
The national average twin rate from IVF has been declining as more clinics adopt SET, but some clinics still routinely transfer 2–3 embryos. A multiple gestation rate above 15% should prompt questions about the clinic's transfer practices.
How to Use These Metrics Together
No single metric tells the whole story. The most informative approach is to build a multi-dimensional profile of each clinic:
- Success rate for your age group — the baseline comparison (how to read success rates)
- SET rate — is the success rate achieved responsibly?
- Volume — is the data statistically meaningful?
- Fresh/frozen mix — does the clinic follow current best practices?
- Lab metrics — ask during consultation for fertilization, blastocyst, and thaw survival rates
A clinic that scores well across all five dimensions is doing something right — and their success rate can be trusted as a genuine reflection of quality, not an artifact of patient selection or aggressive transfer practices.
Start building your shortlist with the PlainFertility clinic rankings, which present multiple metrics side by side for easy comparison.
Frequently Asked Questions
What is a single embryo transfer (SET) rate and why does it matter?
The single embryo transfer rate is the percentage of transfers where only one embryo is placed in the uterus. Higher SET rates indicate a clinic follows evidence-based practices that reduce the risk of twin and triplet pregnancies, which carry serious health complications. A high success rate combined with a high SET rate is a strong quality signal.
How important is clinic volume?
Volume indicates experience but is not a direct quality measure. Clinics performing fewer than 50 cycles per year have small-sample statistics that can swing wildly from year to year. High-volume clinics (500+ cycles/year) have more stable, meaningful data. Some specialized smaller clinics achieve excellent results, but their reported rates are less statistically reliable.
What is the difference between live birth rate and pregnancy rate?
Live birth rate measures cycles resulting in a baby born alive — the outcome patients actually want. Pregnancy rate measures cycles where a positive pregnancy test or ultrasound occurred, but includes pregnancies ending in miscarriage or ectopic pregnancy. Some clinics market their pregnancy rate because it is always higher than the live birth rate. Always use live birth rate for comparisons.
Why does freeze-thaw survival rate matter?
If a clinic freezes embryos using vitrification (the modern standard), thaw survival should be 95% or higher. Lower thaw survival means embryos are being lost in the freezing/thawing process — which means fewer embryos available per cycle and higher costs for additional retrievals. A poor freeze-thaw rate can negate the advantage of a good stimulation protocol.
Should I pay attention to fertilization rate?
Yes, as a laboratory quality indicator. Normal fertilization rate (for ICSI) should be roughly 70–80%. Significantly lower rates may indicate laboratory technique issues. However, fertilization rate alone doesn't predict success — an embryo must develop properly, implant, and result in a live birth. It is one signal among many.
Understanding the Data
The information presented throughout this guide is informed by publicly available public records published by federal and state government agencies. Our database aggregates and standardizes these records to make them more accessible and easier to interpret for general audiences. When we reference specific statistics or trends, they are drawn directly from these authoritative sources unless explicitly noted otherwise.
It is important to understand the limitations of any large-scale data dataset. Records may contain errors from the original data collection process, some fields may be incomplete for older entries, and classification systems may have changed over time. Our analysis accounts for these factors by clearly labeling data vintage, flagging records with missing critical fields, and noting when temporal comparisons span methodology changes in the source data.
For readers who want to conduct their own research, we recommend going directly to the source whenever possible. federal and state government agencies provides detailed documentation on collection methodology, sampling frames, and known data quality issues. Our goal is not to replace primary sources but to make them more approachable and to highlight patterns that may not be immediately obvious when browsing raw records.
How We Analyze Data Records
Our analytical approach involves several steps designed to surface meaningful insights from large datasets. First, we clean and standardize the raw data, handling variations in naming conventions, date formats, and categorical labels. Then we compute summary statistics, distributions, and comparative benchmarks across relevant dimensions such as geography, time period, and category type.
Key metrics we examine include statistical records, geographic distributions, temporal trends. These indicators provide a multi-dimensional view of each entity in our database, allowing users to understand not just individual records but how they compare to peers, regional averages, and national benchmarks. We believe this contextual approach is far more valuable than presenting raw numbers in isolation.
