How to Read a Fertility Clinic's Success Rates (SART vs CDC)

How do you read a fertility clinic's success rates?

Read a fertility clinic's success rates from two public sources, SART and the CDC, and treat the raw percentages with care. A high success rate can reflect a clinic that treats younger, easier patients rather than one that is better. Compare clinics only within the same age band, look at egg-freezing outcomes specifically, and never trust a single blended number.

Clinic success rates feel like they should settle the question of where to go. In practice they are one of the most misread numbers in fertility. The data is real and public, but it is easy to draw the wrong conclusion from it. This is how the two US registries work, what the numbers do and do not tell you, and how to compare clinics honestly. It is also the standard we apply across our verified directory.

What is SART?

SART, the Society for Assisted Reproductive Technology, is the main professional body for US fertility clinics. Its member clinics report every treatment cycle to a shared registry called SART CORS, which publishes clinic-level outcomes.

Because reporting is standardized, a clinic's SART summary report lets you see its activity and results in a consistent format. A clinic that is a SART member and publishes a CORS summary is operating transparently, which is the baseline you want before you look at any number in detail. Not every US clinic is a SART member, so membership itself is a useful first filter.

What is the CDC's fertility data?

Separately from SART, federal law requires fertility clinics to report their ART cycles to the CDC every year. This has been the case since the Fertility Clinic Success Rate and Certification Act of 1992. The CDC then publishes national totals and a report for each reporting clinic.

The two systems overlap heavily but are independent, which is useful: a clinic that appears in both SART and the CDC data has two separate public records of what it does. If a clinic is hard to find in either, that absence is itself worth a question.

Why raw success rates mislead

Here is the trap. A clinic's headline success rate depends enormously on which patients it treats, not only on how well it treats them. A program that mostly serves women under 35 with good ovarian reserve will post higher numbers than one that takes on older or more complex patients, even if the second clinic is technically excellent.

This is called patient-mix or case-mix, and both SART and the CDC warn against using their data to rank clinics because of it. A clinic can also influence its numbers by being selective about who it accepts. So a raw "success rate" comparison between two clinics can reward the one that simply chose easier patients. This is the same reason we refuse to publish a single blended score in our directory, and instead show each clinic's real, separate signals. Our methodology explains that choice in full.

How to compare clinics honestly

You can still learn a lot from the data if you read it carefully.

• Compare within your age band. Both registries break results out by age. Only compare a clinic's numbers for women your age, never the clinic's overall average.
• Look at egg freezing specifically. A clinic's IVF success rate is not the same as its egg-freezing track record. Ask for the metric that matches what you are doing.
• Weigh volume. A clinic doing very few cycles has statistically noisy percentages. More cycles make a rate more meaningful.
• Ask about the denominator. Success "per cycle," "per transfer," and "per patient" are different numbers. Make sure you are comparing like with like.

What the data cannot tell you

The registries measure outcomes, not experience. They will not tell you whether the doctor listens, whether the clinic counsels honestly about your specific odds, or whether the lab shares its egg thaw-survival rate. Those come from the questions you ask and the named, board-certified doctor you verify. The numbers are a filter, not a verdict.

Learning how to read a fertility clinic's success rates mostly means learning what they leave out: they reflect patient mix as much as skill, so they belong beside a verified doctor, an honest lab, and age-specific counselling, not above them. Use SART and the CDC to screen, then use our verified directory and our guide on how to choose a clinic to decide.