To read IVF clinic success rates, first check what the percentage measures: a positive pregnancy test, a clinical pregnancy, or a live birth. Then compare clinics using the same age group, egg source, and treatment stage, such as per embryo transfer or per egg retrieval. Ask whether frozen embryo transfers and later transfers are included, how many patients the rate represents, and what outcome the clinic expects for your situation.
What does an IVF clinic success rate actually mean?
An IVF clinic success rate is a percentage showing how often a particular treatment outcome occurs among a defined group of patients or treatment cycles. However, there is no single percentage that describes every part of IVF treatment. A clinic might report its pregnancy rate, live birth rate, or cumulative chance of having a baby after using embryos from one egg retrieval. Each figure answers a different question.
When you see an advertised success rate, look for two details: the outcome being measured and the group used to calculate it. A rate of 40% per embryo transfer, for example, means that 40 out of every 100 embryo transfers in the reported group resulted in the stated outcome. It does not mean that 40 out of every 100 people who started IVF will necessarily have a baby.
The US Centers for Disease Control and Prevention (CDC) explains that IVF results can be reported at different stages, including intended egg retrieval, actual egg retrieval, and embryo transfer. Understanding which stage a clinic uses is essential before comparing its figures with those of another clinic.
Which IVF success rate should you look at first?
For most people choosing a fertility clinic, the live birth rate is one of the most meaningful measures because it focuses on whether treatment results in a birth, rather than stopping at an earlier stage. However, you should also check how the rate was calculated and whether it reflects the full treatment process or only patients who reached embryo transfer.
Live birth rate
The live birth rate is the percentage of eligible patients, treatment cycles, retrievals, or embryo transfers that result in a live birth, depending on the measure used. It is different from a pregnancy rate because a pregnancy does not always result in a live birth. When comparing clinics, check whether they report live births per cycle started, per egg collection, per embryo transfer procedure, or per embryo transferred.
Pregnancy rate
A pregnancy rate measures how often a treatment reaches a defined pregnancy outcome. The exact definition can vary: some reports measure clinical pregnancies, while others use different pregnancy milestones. A positive pregnancy test is not the same as a confirmed clinical pregnancy, and neither automatically means a live birth. Ask the clinic which definition it uses and whether the figure refers to fresh transfers, frozen transfers, or both.
Cumulative live birth rate
A cumulative live birth rate estimates the chance of achieving a live birth after using embryos from one egg retrieval, including multiple transfers within a specified period. For example, an initial fresh embryo transfer may not result in a birth, but a later frozen embryo transfer from the same retrieval may. A cumulative figure can account for these later opportunities that a single-transfer rate does not capture.
Check the time window and the transfers included. The CDC's reporting system, for example, presents cumulative success rates for patients using their own eggs based on transfers occurring within one year after an egg retrieval. Other reporting systems may use different definitions or periods. A cumulative rate is meaningful only when you know what treatment and follow-up it covers.
How do per-cycle, per-retrieval, and per-transfer rates differ?
The denominator is the number of treatment starts, retrievals, transfers, or other events used to calculate the percentage. This number matters because not everyone who starts IVF reaches the embryo transfer stage.
- Per cycle started: Counts treatment cycles from the beginning, generally when ovarian stimulation or monitoring starts with the intention of retrieving eggs. This can include cycles that are cancelled before retrieval or transfer.
- Per egg retrieval: Counts procedures in which eggs are collected. It excludes cycles that stop before an egg retrieval takes place.
- Per embryo transfer procedure: Counts procedures in which one or more embryos are transferred. It does not include cycles that never reach transfer.
- Per embryo transferred: Counts individual embryos transferred rather than transfer procedures. The denominator is therefore different when a procedure involves more than one embryo.
Consider a hypothetical example. Clinic A reports 30 live births per 100 treatment cycles started, while Clinic B reports 40 live births per 100 embryo transfer procedures. Clinic B's percentage is higher, but the figures are not directly comparable. Its denominator excludes patients whose cycles did not reach transfer. You would need comparable measures from both clinics before deciding which has the stronger results for your circumstances.
The UK Human Fertilisation and Embryology Authority (HFEA) explains the differences between birth rates per egg collection and per embryo transfer and notes that clinic statistics cannot predict an individual patient's chance of having a baby.
Why does age matter when comparing IVF clinic success rates?
Age is an important factor in IVF success, particularly when a person uses their own eggs. The age group represented in a clinic's results can substantially affect its reported percentage. A clinic treating mostly younger patients may have a higher overall success rate than one treating more older patients, even when the figures do not establish that one clinic provides better care.
For IVF using your own eggs, look for results in an age group that closely matches your age when the eggs are collected, and confirm how the reporting system defines age. Broad age categories can conceal meaningful differences between patients. If you are comparing clinics, try to use figures from the same age band rather than relying on a clinic's overall headline percentage.
Donor eggs or donor embryos require a separate comparison. Their results should not be treated as equivalent to outcomes using a patient's own eggs. The age of the person providing the eggs and the treatment approach affect how those statistics should be interpreted. A clinic that performs more donor-egg treatments may report a higher overall rate than a clinic that treats a different patient group.
The CDC's ART success-rate reporting tool separates outcomes by patient age and egg or embryo source. Use the relevant category rather than a clinic-wide figure, and compare results from the same reporting year when possible.
What other details can change the comparison?
Are fresh and frozen embryo transfers counted separately?
Fresh and frozen embryo transfers may be reported separately or together. A frozen transfer uses an embryo that was frozen for later treatment, while a fresh transfer takes place during the original treatment sequence. Clinics may differ in how frequently they use each approach, so check which transfer types are included before comparing their results.
Are the results for your own eggs or donor eggs?
Confirm whether a reported percentage includes only patients using their own eggs or also includes donor eggs and donor embryos. Combining these groups can make the headline figure less relevant to your treatment plan. Ask whether the clinic can provide separate live birth rates for the egg or embryo source you expect to use.
Do the figures include cycles that never reach embryo transfer?
A clinic's results may look different depending on how it handles cancelled cycles and patients who do not have an embryo available for transfer. A rate calculated only among completed transfers leaves out earlier stages of treatment. Ask how many people started treatment, how many reached egg retrieval, how many had embryos available, and how many proceeded to transfer. These figures help you understand what the headline rate leaves out.
Does embryo testing affect the reported rate?
Some clinics use preimplantation genetic testing for aneuploidy (PGT-A), which checks embryos for abnormal chromosome numbers. Testing strategies and the way patients are counted can affect comparisons. For example, a statistic limited to embryos that reach transfer may not reflect everyone who began treatment but had no embryo available for transfer after testing. Ask whether testing cycles are included and whether the published outcome applies to patients with a similar treatment plan.
When a clinic promotes an add-on as the reason for unusually high success rates, ask for evidence that it improves the chance of a live birth for patients like you. The HFEA's explanation of IVF clinic statistics discusses how the use of donor eggs, embryo testing, and differing treatment practices can make clinic comparisons more difficult.
How reliable are a clinic's published results?
Look at the number of treatment cycles behind the percentage. A high rate based on a small group can change considerably when only a few additional outcomes are recorded. A larger group generally gives a more stable estimate, although it still does not predict an individual patient's result.
Also check the reporting year. Live birth results take time to compile because treatments must be completed, births followed up, and information collected and reviewed. As a result, published outcomes may describe treatments performed more than a year earlier. Staffing, laboratory procedures, and clinical practices may have changed since then.
Prefer official reporting systems that explain their methods and apply consistent definitions across clinics. In the United States, the CDC publishes clinic-level assisted reproductive technology data. In the United Kingdom, the HFEA provides information on licensed clinics. These systems are designed for their respective countries, so use the appropriate national regulator or recognised reporting body where you plan to receive treatment.
Can the clinic with the highest success rate be the best choice?
Not necessarily. Success rates reflect both treatment outcomes and the characteristics of the patients being treated. Clinics may differ in the ages and diagnoses of their patients, the use of donor eggs, and the types of treatment they offer. Some may accept a wider range of patients, including people whose predicted chance of success is lower. Others may have small numbers of cases in a particular category.
The HFEA advises patients not to rely on success rates alone when choosing a clinic. Consider whether the team explains the statistics clearly, provides transparent costs, offers appropriate counselling and follow-up, and discusses your treatment options without promising a particular outcome. Clear communication and an individualised treatment plan are more useful than a headline percentage on its own.
What should you ask an IVF clinic about its success rates?
Bring the clinic's published figures to your consultation and ask the team to explain them in plain language. These questions can help you understand whether the numbers reflect the treatment you are considering:
- Is the reported percentage a pregnancy rate or a live birth rate?
- Is it calculated per cycle started, per egg retrieval, per embryo transfer procedure, or per embryo transferred?
- Does the figure match my age group and the use of my own eggs or donor eggs?
- Are fresh and frozen embryo transfers reported separately?
- Does the cumulative rate include later transfers from the same egg retrieval, and over what period?
- How many patients or treatment cycles contributed to the published figure?
- What percentage of patients starting treatment reach egg retrieval and embryo transfer?
- How do you estimate my chance of a live birth based on my medical history and planned treatment?
- What are the clinic's multiple birth rates, and what steps are taken to reduce the chance of a multiple pregnancy?
Request an estimate based on your age, treatment history, fertility assessment, and planned use of eggs or embryos. The CDC IVF Success Estimator is one example of a tool that uses characteristics of patients with similar backgrounds to estimate the chance of a live birth. It is an educational estimate, not a guarantee or a replacement for your clinician's assessment.
How can you compare two IVF clinics fairly?
Start by putting each clinic's results on the same basis. Compare live birth rates for the same age group, egg or embryo source, treatment stage, and reporting period. Check whether the statistics include frozen transfers, cumulative outcomes, and patients who do not reach embryo transfer. Record the number of cases behind each result and look for any explanation of the clinic's patient population or reporting method.
Next, use the figures as a starting point for questions rather than as a final ranking. A clinic with a slightly lower published rate may treat a different group of patients or may report its results using a broader denominator. Ask each clinic to explain its data and give an estimate tailored to your treatment plan.
The most useful success rate is the one that measures a meaningful outcome in a patient group similar to yours. Read the definition, check the denominator, account for age and egg source, and consider the full treatment journey. Combined with transparent information about care, safety, cost, and support, these steps can help you make a more informed decision about an IVF clinic.