Understanding IVF Success Rates: How They Are Measured
Key Takeaways
IVF success can be counted in several ways: per cycle started, per egg collection, per embryo transfer, or across all transfers from one egg collection. Two clinics can quote very different numbers for the same patient. In its 2019 report, ESHRE/EIM found a clinical pregnancy rate of about one in three per fresh transfer. That is an average for many patients, not a forecast for you. To read any figure, check what was counted, who was included, the age group and your own medical factors.
Key evidence: ESHRE/EIM — ART in Europe, 2019 SART — National Summary Report (2023 US Data) ASRM Practice Committee — Ovarian Reserve & Prognosis (2020)
When patients ask me, “Doctor, what is your success rate?”, I know what they are hoping for: one clear, reassuring number to hold on to. I wish the answer were that simple. It is a natural question, and one of the easiest to answer in a misleading way.
The truth is that “IVF success rate” is not one figure. It is a family of different measurements. The number a clinic shows on its website depends on which measure it picks and which patients it counts. Before you compare clinics or plan treatment, it helps to know what these numbers describe, and what they cannot tell you about your own chances.
Why IVF success rates are not a single number
There is no single “success rate”, because results can be counted at different points in treatment. Each point gives a different percentage:
- Per cycle started: Counts every patient who starts the medicines that stimulate the ovaries, including those who cancel before egg retrieval.
- Per egg retrieval (egg collection): Counts patients who reached egg collection. Early cancellations are left out.
- Per embryo transfer: Counts only patients who reached transfer with an embryo to transfer. This figure can look higher, because cancelled stimulations and cycles with no transferable embryo drop out of the group being counted (the denominator). It cannot be compared directly with a rate per cycle started.
- Cumulative live birth rate (CLBR): The chance of a live birth across all fresh and frozen embryo transfers from one egg retrieval.
The term pregnancy rate needs a definition too. It may mean a biochemical pregnancy, confirmed by a positive hCG test, or a clinical pregnancy (one confirmed by ultrasound). A live birth rate counts a baby born alive. For the same group of patients, the live birth rate is usually lower, because some pregnancies end before birth.
Three questions help you read any figure:
- Is this number per cycle started, per retrieval, or per transfer?
- Does “pregnancy” mean a biochemical pregnancy, a clinical pregnancy seen on ultrasound, or a live birth?
- Which age group does this percentage cover?
Without these three answers, a single percentage tells you very little.
How clinics report outcomes — and what to compare
To compare two clinics fairly, check that they measure the same outcome in the same way, in similar groups of patients.
These points matter most:
- Registry versus in-house data: National and European registries use standard definitions. Statistics on a clinic’s marketing pages may count a more selective group.
- Per transfer versus per retrieval: Per-transfer figures leave out patients who never had a transferable embryo. That can make a clinic’s headline rate look higher than its rate per retrieval.
- Fresh versus frozen transfer: Results after frozen transfer are shaped by which patients were chosen, freeze-all policies, embryo stage and the timing of transfer. In randomised trials (where chance decides which strategy a patient gets), pooled results suggest little or no difference in cumulative live birth between a freeze-all strategy and conventional treatment. The choice can still make sense in specific clinical situations. See our guide on fresh versus frozen embryo transfer and the Cochrane review on fresh versus frozen transfer.
- Cumulative live birth rate (CLBR): Useful for a whole egg retrieval, if the retrieval, linked transfers, follow-up period and group counted are clearly defined. Two CLBR figures from different registries are not automatically comparable.
- Age breakdown: Maternal age is a major biological factor in IVF outcome. A statistic with no age breakdown is hard to apply to one patient.
Higher overall rates do not necessarily mean better care. A clinic that treats mostly younger patients with simpler diagnoses will naturally show higher rates, while a specialist centre that treats older patients and patients with low ovarian reserve or repeated implantation failure will show lower ones.
What European registry data show
European registry averages depend on what is measured and who is counted. The pregnancy and delivery rates below are calculated per embryo transfer, not per started cycle.
The European IVF Monitoring Consortium (EIM), coordinated by the European Society of Human Reproduction and Embryology (ESHRE), collects national registry data from across Europe. In its report on 2019 cycles, the clinical pregnancy rate per fresh transfer was 34.6% for conventional IVF and 33.5% for ICSI. Delivery rates per transfer were 25.3% and 24.1%. Frozen embryo transfers had a clinical pregnancy rate of 35.8% and a delivery rate of 25.6% per transfer. These are averages from many European centres, not a forecast for one clinic or one patient.
| Measure (European registry, per transfer) | IVF | ICSI | Frozen transfer (FET) |
|---|---|---|---|
| Clinical pregnancy rate | ~34.6% | ~33.5% | ~35.8% |
| Delivery rate | ~25.3% | ~24.1% | ~25.6% |
Source: ESHRE/EIM European Registry Report on 2019 cycles. These are European multi-centre averages per embryo transfer, not figures for any one clinic.
These averages hide a strong age pattern. Outcomes tend to be higher in younger age groups and lower after 40, but biology does not change on one exact birthday. Read the ESHRE report as a summary of a population, not as a personal forecast (see our article on IVF and age limits after 40).
The ESHRE/EIM report on 2020 cycles found pregnancy rates after fresh IVF, fresh ICSI and frozen transfer similar to 2019, while the number of reported cycles fell by 14%. The preliminary ESHRE/EIM data for 2022, shown as a conference abstract in 2025, describe IVF and ICSI pregnancy rates as similar to 2021, with a slight fall after frozen embryo transfer. These figures are preliminary and may still change. They are also given per egg collection, per transfer and per thawing, so we have not added them to the 2019 per-transfer table.
A US benchmark for context
US national data add a second view. They report outcomes per intended egg retrieval, including linked embryo transfers within the report’s follow-up period.
The Society for Assisted Reproductive Technology (SART) reports US national outcomes. For 2023 cycles using patients’ own eggs, the live birth rate per intended egg retrieval after all embryo transfers fell steadily as age rose:
| Maternal age | Live birth rate per intended retrieval, all embryo transfers (US SART, 2023) |
|---|---|
| Under 35 | 53.2% |
| 35–37 | 39.9% |
| 38–40 | 26.2% |
| 41–42 | 13.2% |
| Over 42 | 4.1% |
Source: SART National Summary Report, 2023 cycles, own eggs. The all-transfer figure combines the first and later linked transfers within the report’s follow-up window, and includes cycles that never reached transfer, so it differs in method from the European per-transfer table. SART notes that COVID-19 delayed some embryo transfers, which left more cycles without a transfer within 12 months of retrieval and lowered overall live birth rates per cycle.
European and US registries group their data differently, so they cannot be compared directly. Both show a strong age pattern. Age is a major biological predictor, but neither table decides what will happen for one patient.
What actually determines your individual odds?
A registry average describes a large population. Your own prognosis depends on a mix of clinical and biological factors:
- Maternal age: Strongly affects the chance that an embryo has the normal number of chromosomes (is euploid).
- Ovarian reserve (AMH and antral follicle count): Helps estimate how the ovaries will respond and how many eggs we may retrieve. It does not measure egg quality directly. It should not be used alone to predict live birth, as the ASRM committee opinion on ovarian reserve explains. Our guide on how many eggs you need for IVF success explains why more eggs give more chances of reaching a transferable embryo.
- Semen analysis and selected male-factor tests: Sperm concentration, forward movement (progressive motility) and shape (morphology) are checked routinely. Testing for sperm DNA damage (fragmentation) is not recommended as a routine first test. The AUA/ASRM male infertility guideline, first published in 2020 and amended in 2024, does not recommend it in the initial evaluation of the infertile couple.
- Prior cycle response: How your ovaries responded to stimulation before, and how many eggs fertilised and developed into blastocysts.
- Uterine and endometrial health: The shape of the womb cavity, and whether polyps or fibroids bulge into it (submucosal fibroids). Good preparation of the lining in frozen embryo transfer protocols also matters.
- Embryo development and genetics: Blastocyst expansion grades and, where clinically indicated, preimplantation genetic testing.
Because these factors interact, two women of the same age can have quite different prognoses.
Dr. Aksoy’s Approach
Dr. Aksoy’s approach: realistic planning, not marketing percentages
“When a patient asks me, ‘Another clinic advertises a 70% success rate, what is yours?’, my first question is: 70% of what? Is that a positive pregnancy test, a single transfer of a selected blastocyst, or a cumulative live birth rate after using fresh and frozen embryos from one retrieval? These are different clinical endpoints.
Clinic-wide headline rates also depend heavily on patient selection and age distribution. In consultation, I focus on two numbers: the realistic live birth probability per transfer, and the cumulative live birth probability across the embryos from that retrieval within a defined follow-up period.
Age is a major predictor because it is closely related to the probability that an embryo is chromosomally euploid. AMH, on the other hand, helps us estimate ovarian response and how many eggs we may obtain; it informs the likely length and demands of the process, not a simple ‘yes or no’ test of pregnancy. Between two patients of the same age, prognosis also reflects stimulation response, blastocyst yield, embryo genetics, sperm factors, prior IVF outcomes, and uterine or endometrial health.
If a patient asks, ‘Will it definitely work on the first try?’, I explain that I cannot promise this. A negative first cycle does not mean the treatment plan is exhausted. A clear, evidence-based plan helps us manage uncertainty step by step.”
— Dr. Senai Aksoy
Related reading
- Fresh vs. Frozen Embryo Transfer: What the Evidence Shows
- How Many Eggs Do You Need for IVF Success?
- Decoding Your IVF Lab Report: Embryo Grading Explained
Frequently Asked Questions for Dr. Aksoy
How does the chance of IVF success change with age?
Age is one of the first things I look at when I assess the chance of success with IVF. In the early thirties we usually expect a higher chance. Between 35 and 38 the chance gradually falls, and after 40 the fall is more marked, mainly because chromosomal abnormalities in the eggs become more common.
But I do not assess patients by age alone. I also consider ovarian reserve, the results of earlier treatment and how the embryos we obtain develop. One thing I make a point of explaining: a good AMH value does not mean the eggs are necessarily of good quality. So the same success rate does not set the same expectation for a 32-year-old woman and a 42-year-old woman.
What should I look at in a clinic’s IVF success rate, and what should I ask the clinic?
For me the most meaningful measure is not a positive pregnancy test but the live birth rate. How that rate was calculated matters just as much. Does it count only patients who had an embryo transfer, or also patients who started treatment but had no eggs or embryos? That is worth checking.
I suggest that patients ask clinics for the results of women in their own age group who were treated with their own eggs. It is also important to ask for the total success of all the transfers made with the embryos from a single egg collection.
A clinic’s high success rate on its own is not enough. What matters is which patients the figure covers and how well it fits your situation.
Frequently asked questions
Is a higher “pregnancy rate” the same as a higher chance of a live birth?
No. Depending on the registry, a pregnancy rate may mean a positive β-hCG test or a clinical pregnancy confirmed by ultrasound. A live birth rate counts babies born alive. Do not compare the two until you know how each was defined and who was counted.
What is a cumulative live birth rate (CLBR)?
It is the chance of a live birth across the fresh and frozen embryo transfers from one egg retrieval, within a stated follow-up period. It can be a useful measure for a whole retrieval. Before you compare two CLBR figures, you need to know the time window and the group counted.
Can my doctor predict my exact personal success rate before treatment begins?
A clinician can give you a personal range based on your age, ovarian reserve tests (AMH and antral follicle count), semen analysis and medical history, but it cannot be a guarantee.
Sources
- Smeenk J, Wyns C, De Geyter C, et al. ART in Europe, 2019: results generated from European registries by ESHRE. Human Reproduction 2023;38(12):2321–2338.
- Smeenk J, Wyns C, De Geyter C, et al. ART in Europe, 2020: results generated from European registries by ESHRE. Human Reproduction 2025;40(11):2038–2055.
- de Neubourg D, Smeenk J, Cuevas I, et al. Assisted Reproductive Technology (ART) in Europe 2022: preliminary results generated from European registers by the ESHRE EIM consortium. Conference abstract O-159. Human Reproduction 2025;40(Suppl 1):deaf097.159.
- Society for Assisted Reproductive Technology (SART). National Summary Report (2023 Data).
- Practice Committee of the American Society for Reproductive Medicine (ASRM). Testing and interpreting measures of ovarian reserve: a committee opinion. Fertility and Sterility 2020;114(6):1151–1157.
- Schlegel PN, Sigman M, Collura B, et al. Diagnosis and treatment of infertility in men: AUA/ASRM guideline part I. Fertility and Sterility 2021;115(1):54–61.
- Brannigan RE, Hermanson L, Kaczmarek J, et al. Updates to male infertility: AUA/ASRM guideline (2024). Journal of Urology 2024;212(6):789–799.
- Zaat T, Zagers M, Mol F, et al. Fresh versus frozen embryo transfers in assisted reproduction. Cochrane Database of Systematic Reviews 2021;2:CD011184.
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The content has been created by Dr. Senai Aksoy and medically approved.