How to Compare IVF Success Rates Without Getting Fooled by the Denominator
Retrieval, transfer, clinical pregnancy and live birth are different metrics. Learn what a clinic success-rate claim actually measures.
A percentage is meaningless until you know the denominator
“70% success” could mean fertilization, blastocyst development, pregnancy per transfer, clinical pregnancy, ongoing pregnancy or live birth. Those are different outcomes at different stages.
CDC’s ART reporting framework illustrates why the denominator matters: outcomes can be reported per intended retrieval, actual retrieval or embryo transfer, and cumulative measures can include later transfers from the same retrieval.
Patient mix changes clinic statistics
Age, diagnosis, prior ART history, use of donor eggs and treatment choices all affect outcomes. A clinic that accepts difficult cases can appear worse than a clinic that selects lower-risk patients.
CDC explicitly cautions that average success rates may not represent the chance for an individual patient. That warning applies even more strongly when comparing a Colombian clinic’s marketing statistic with a U.S. registry statistic built under a different reporting system.
Ask for the exact population
When a clinic gives you a rate, ask the year, age group, whether own or donor eggs were used, whether the metric is per retrieval or transfer, and whether it is pregnancy or live birth.
If the coordinator cannot define the statistic, do not use it to choose between clinics.
Your personal estimate belongs in a consultation
A real physician can discuss how your age, ovarian reserve, diagnosis, prior cycles and treatment plan affect prognosis. A marketing page cannot responsibly convert one clinic-wide percentage into your personal chance of success.
Use statistics to ask better questions, not to self-prescribe a clinic.
Questions worth sending the clinic
- What exactly does your published success percentage measure?
- Is it per retrieval, per transfer, or cumulative?
- Is the outcome pregnancy or live birth?
- Which age group and egg source does it describe?
- What year and number of cycles are included?
Want help figuring out the next step?
Use email or WhatsApp. Everything else is optional. Please keep detailed medical records for a clinic's secure clinical channel.
Sources & verification
Cross-border treatment rules, clinic policies and evidence reviews can change. Re-check primary sources and the clinic's current written policy before making a decision.