Imagine a coin that's slightly weighted toward heads. If you flip it 10 times, you might get 8 heads — an 80% rate. But that doesn't mean the coin is 80% likely to land heads on your next flip. With a small sample, random variation can produce misleading results.

IVF success rates work the same way. A clinic that treated 15 patients under 35 last year and had 11 live births reports a 73% success rate. But that rate is based on such a small sample that it tells you very little about what you can expect as patient number 16.

How much volume is enough?

There's no perfect threshold, but here are reasonable guidelines by age group:

Cycles in your age group Statistical reliability
Fewer than 20 CDC suppresses the rate entirely — too unreliable to publish
20–50 Rate is published but should be treated with significant caution
50–100 Directionally useful — worth considering alongside other factors
100–200 Reasonably reliable — rate reflects real patterns
200+ High confidence — this clinic has seen enough cases to produce meaningful statistics

Why the CDC suppresses some rates

When a clinic performs fewer than 20 cycles in an age group, the CDC doesn't publish a percentage — it shows a fraction instead (like 3/8) or suppresses the data entirely. This is deliberate. A percentage calculated from a handful of cases is statistically meaningless and potentially misleading.

On FertilityMetrics, when you see "N/A" or "Insufficient data" for an age group, this is why. It's the CDC's way of saying: there isn't enough data here to draw conclusions.

High volume doesn't always mean better care

Volume and quality aren't the same thing — but they're related. Clinics that perform more cycles tend to have more experienced embryology teams, more refined protocols, and more exposure to complex cases. Repetition builds skill in highly technical procedures.

However, very high-volume academic medical centers sometimes serve a disproportionate share of difficult cases — patients who've failed elsewhere, patients with complex diagnoses, older patients. This can make their raw success rates look lower than a smaller boutique clinic, even if their clinical skill is equal or superior.

Use volume as a filter for statistical reliability, not as the sole measure of clinic quality.

The patient mix problem

Two clinics can have identical volumes and dramatically different success rates because of who their patients are. A clinic that primarily serves 25–32 year olds with unexplained infertility will report higher rates than one that specializes in complex cases, recurrent pregnancy loss, or patients over 40. The difference reflects patient selection, not necessarily clinical skill.

This is why the CDC breaks rates down by age group — it partially controls for this. But age alone doesn't capture diagnosis complexity. When comparing clinics, look at the diagnosis breakdown on each clinic page to understand what kinds of cases they see most frequently.

What to ask the clinic

When you're reviewing a clinic's success rates, ask: "How many patients did you treat in my age group last year?" If the answer is fewer than 50, treat their reported rate as a rough data point rather than a reliable prediction.

The combination of a solid rate and meaningful volume is the most reliable signal available in public IVF data.