You open a clinic's success rate table and see a wall of percentages, age bands, and footnotes. One number looks great, another looks mediocre, and nothing tells you which one applies to you. The problem is rarely that the data is wrong. It is that a success rate is a fraction, and the table usually shows you the top of the fraction without making the bottom easy to find.
This guide walks through how to read those tables in order, so each percentage you look at is answering a question you actually asked.
In the SART national summary for 2023, what was the live birth rate per intended egg retrieval for patients under 35 using their own eggs?
Select one answer.
Start with the denominator, not the percentage
A success rate is live births divided by some denominator. Which denominator a clinic uses changes the number substantially, and tables do not always make the choice obvious. The CDC tracks IVF cycles using different denominators depending on how far a cycle progresses, including intended retrieval, actual retrieval, and transfer.
Before you compare two percentages, find out what each one is divided by. A live birth rate per transfer and a live birth rate per intended retrieval are not the same measure, even when they sit side by side in a report.
Know which outcome is being counted
Tables may report positive pregnancy tests, clinical pregnancies confirmed by ultrasound, or live births. These are three different milestones, and only live birth reflects a delivery. The SART national summary reports live births per intended egg retrieval, broken out by age band, which makes it a useful reference point for what the standard measure looks like.
When a clinic's own page leads with a pregnancy rate, check whether a live birth rate appears elsewhere in the same table.
Match the age band and cycle type to your situation
Age at egg retrieval is the major predictor of IVF outcome, and success declines as patients move through their reproductive years. A rate from a younger cohort does not describe an older patient's odds.
Cycle type matters just as much. Tables typically separate patients using their own eggs from donor-egg cycles, and they separate fresh transfers from frozen ones. Donor-egg data is often not broken down by recipient age, because the egg age drives the result. If your situation involves donor eggs, read the donor-egg rows, not the headline.
Check the sample size behind the number
A percentage built on a small number of cycles is far less stable than one built on hundreds. Look for the cycle count column, not just the rate column. A strong-looking figure from a thin denominator deserves less weight in your comparison.
Look for the year and the reporting lag
Live birth data takes time to verify, so published reports describe a past year rather than the current one. The CDC's ART success rates data is organized by reporting year for this reason. A clinic's strong year is not the same as a current pattern, so check which year each figure covers before treating it as present-day performance.
Expect two numbers for the same clinic
A clinic's website may advertise one figure while its official report shows another for the same year. Neither is necessarily wrong; they are answering different questions. One may be per transfer, the other per retrieval, or one may cover a single age band while the other covers all patients.
SART itself advises caution about comparing clinics on statistics alone, because patient selection and treatment approaches vary between programs. Some clinics treat more complex cases; others see patients with better prognoses. That difference shows up in the numbers without appearing in the table.
A checklist to run on any table
- Find the denominator. Is the rate per transfer, per retrieval, or per patient?
- Identify the outcome. Positive test, clinical pregnancy, or live birth?
- Match your age band. Read the row for your age at retrieval, not the overall figure.
- Check cycle type. Own eggs or donor eggs? Fresh or frozen transfer?
- Note the cycle count. How many cycles is the percentage built on?
- Confirm the year. Which reporting year does this figure describe?
- Reconcile discrepancies. If two numbers differ, look for a definitional reason before assuming an error.
What the table cannot tell you
A success rate does not capture the lab, the doctor relationship, the cost, or how a clinic handles a failed cycle. Those belong in your consultation questions, not in a spreadsheet column. Use the table to narrow your list and to ask sharper questions, then weigh the parts of care that no percentage holds.
How the Featured Expert Can Help
Fertility X-Ray produces plain-English reports on U.S. fertility clinic success rates, turning CDC data into detailed dossiers for patients. The service sells individual clinic reports and comparative analyses for a fee, aimed at helping prospective patients understand what each number measures before they choose. You can explore the reports at getfertilityxray.com.
Quiz: test your table-reading skills
Before you close this tab, check one fact that anchors everything above. In the SART national summary for 2023, what was the live birth rate per intended egg retrieval for patients under 35 using their own eggs?
If you answered about 53%, you have the reference point you need: every other percentage you read should be checked against its own age band, denominator, and year before you compare it.