By Dr. Shweta Agarwal, MBBS, DGO Medically reviewed by Dr. Shweta Agarwal, MBBS, DGO Last updated: June 2026
Information on this page is educational and does not replace a medical consultation. Outcomes depend on individual clinical factors.
Aansh Hospital & IVF Center is a government-registered Level-2 ART clinic (Reg. No. MH/AC/2024/15441/L2/Chandrapur/132), part of a growing chain of fertility centers across Vidarbha and northern Telangana, with our headquarters and in-house embryology lab in Chandrapur. You can verify our government ART registration directly on the National ART & Surrogacy Registry.
When couples come to our clinic asking about IVF success rates — often after reading a brochure or clinic website — they have almost always been given one number with no context. That number might be 60%, 70%, or higher. It may look impressive. But without knowing exactly how it was calculated, a quoted success rate cannot tell you anything reliable about your own chances.
This is not about suspecting dishonesty. It is about the fact that IVF outcome data is genuinely complex, and that responsible reporting requires several layers of context that are simply not possible to capture in a single headline figure. The goal of this post is to give you the vocabulary and the checklist to evaluate any figure you encounter — including anything we may discuss in your consultation.
The Marathi phrase आयव्हीएफ यश दर म्हणजे काय ("what does the IVF success rate mean?") is one of the most common questions we hear from patients in our Vidarbha and Telangana centres, and it deserves a thorough answer in plain language.
Why does the denominator matter so much?
The denominator — the "per what" of the percentage — is the single most important piece of context behind any success-rate figure, and it is almost never stated in promotional material.
The same clinic, with exactly the same patient cohort and exactly the same outcomes, can produce three very different percentages depending on which denominator is chosen:
Per cycle started: includes every patient who began ovarian stimulation, even those whose cycles were cancelled before egg retrieval because the ovarian response was inadequate or excessive. This is the most conservative and clinically honest denominator. A cycle started that ends without egg retrieval still counts in the denominator but contributes zero to the numerator.
Per egg retrieval: excludes cancelled cycles. Because the denominator is smaller (only patients who reached retrieval), the resulting percentage is higher than per-cycle-started — even if outcomes are identical.
Per embryo transfer: excludes both cancelled cycles and cycles that produced no suitable embryo to transfer. The denominator is smallest of all three, and the resulting percentage is highest — again, even with no change to underlying outcomes.
If a quoted figure does not specify which of these denominators was used, you cannot compare it honestly against any other figure. Published data from large fertility registries routinely shows substantial differences between these three measurements for the same data set.
The internationally recommended standard for reporting, used by registries such as the Human Fertilisation and Embryology Authority (HFEA) in the UK and similar bodies in other countries, specifies the denominator explicitly alongside every published figure. Any claim that omits it should be treated as incomplete.
What does "success" actually mean — clinical pregnancy vs live birth?
The second hidden variable is the definition of "success" used in the numerator.
Positive pregnancy test (biochemical pregnancy): a detectable level of beta-hCG in the blood after transfer. This is the most optimistic measure and the easiest to achieve — but a biochemical pregnancy includes pregnancies that fail before ultrasound confirmation, sometimes called chemical pregnancies. Quoting this as a success rate overstates meaningful outcomes.
Clinical pregnancy rate: a pregnancy confirmed by ultrasound — a gestational sac, and ideally a fetal heartbeat, visible at 6–7 weeks. This excludes early biochemical losses but still includes pregnancies that later end in miscarriage. A clinical pregnancy rate will always be higher than a live birth rate for the same cohort.
Ongoing pregnancy rate: pregnancy still continuing at a specified point, usually 10–12 weeks. This filters out most first-trimester losses but still does not confirm a baby was born.
Live birth rate: a baby born alive. This is the only figure that answers the question patients are actually asking. It is also the most conservative and the most important. In published international registry data, the live birth rate per transfer is lower than the clinical pregnancy rate for the same cohort because it accounts for all pregnancy losses through to birth.
When a clinic quotes "success," always ask: success by which definition? If the answer is "positive pregnancy" or "clinical pregnancy," mentally lower the number to account for the gap between that figure and live birth. If they cannot tell you the definition, the number is not useful for decision-making.
Why is age the dominant variable — and what are age bands?
Female age is the single largest driver of IVF outcome variation, and it operates primarily through egg quality. As a woman ages, the proportion of eggs with chromosomal abnormalities increases — meaning fewer viable embryos result from each retrieval, and fewer transfers lead to healthy ongoing pregnancies.
The practical consequence is this: a success-rate figure pooled across all patient ages is dominated by the age distribution of the clinic's patient mix. A clinic that sees a high proportion of younger patients will naturally post higher pooled numbers than a clinic seeing predominantly older patients, even if both clinics provide identical quality of care for every age group.
This is why the international reporting standard requires outcomes to be presented in age bands — typically under 35, 35–37, 38–39, 40–42, 43–44, and 44 and over. Within each age band, the figures become a much more honest comparison across clinics or against published norms.
Published data from international registries shows that live birth rates per transfer decline substantially across these age bands, with the most pronounced change occurring from age 37–38 upward. Any honest discussion of IVF outcomes must frame expectations within the patient's own age band.
At Aansh, Dr. Shweta Agarwal discusses realistic, age-appropriate, per-transfer expectations during consultation rather than advertising a single pooled figure.
What is the difference between fresh and frozen transfer success rates?
A single IVF cycle can produce multiple embryos. Not all of them are transferred at once — surplus good-quality embryos are vitrified (flash-frozen) and stored for future frozen embryo transfer (FET) cycles. This means a single egg-collection cycle can generate multiple transfer attempts over time.
A fresh transfer uses an embryo transferred in the same cycle as egg collection, usually around Day 3 or Day 5–6 after retrieval. A frozen transfer uses a vitrified embryo from a previous cycle, thawed and transferred in a later, hormonally prepared cycle.
Reporting only fresh transfer rates, or only frozen transfer rates, gives an incomplete picture. In some patient populations and clinic settings, frozen transfers actually post comparable or higher success rates than fresh transfers — partly because the uterine environment after stimulation has had time to recover, and partly because freeze-all strategies (particularly for patients at risk of ovarian hyperstimulation syndrome, including those with PCOS) have become increasingly used.
When comparing figures, always establish: is this a fresh transfer rate, a frozen transfer rate, or a combined figure? And if combined, in what proportions?
What is a cumulative success rate — and is it the most honest figure?
The per-transfer rate answers: "given one transfer attempt, what are the chances?" The cumulative rate answers: "given one egg collection cycle — including all transfers from the embryos generated — what are the overall chances of a live birth?"
Cumulative rates are typically higher than per-transfer rates because they give credit for all usable embryos from a single retrieval. For a patient who has three good blastocysts frozen, the cumulative live birth rate from that single collection cycle (summing the probability across all three eventual transfers) is meaningfully higher than the probability from any single transfer.
Cumulative rates are arguably the most patient-relevant figure for planning purposes — they address the question "what are my chances from this cycle?" rather than "what are my chances from this single transfer?" However, they require multi-year follow-up data to calculate accurately (since the last frozen embryo from a retrieval may not be transferred for one or two years), and they are therefore harder to report in a timely way.
Ask any clinic offering a success rate: is this per transfer, or cumulative? If cumulative, how was it calculated and over what time window?
What is case-mix bias — and why can patient selection inflate numbers?
This is the most misunderstood variable of all. Patient-selection bias — or case-mix — is the effect of which patients a clinic accepts on its reported outcomes.
IVF outcome is powerfully influenced by the patient's starting prognosis. A clinic that primarily treats younger patients with good ovarian reserve and no complex uterine or male factors will tend to post higher success rates than a clinic that accepts all comers, including patients with diminished ovarian reserve, advanced age, multiple failed cycles, or complex conditions. Yet the second clinic may be providing a higher standard of care precisely because it is not turning away difficult cases.
There is no single number that corrects for this. The only way to assess it is to ask: what is the patient mix? Does the clinic accept patients who have already failed multiple cycles elsewhere? What is the policy on age limits? Does the clinic also treat patients with severe male-factor infertility, low AMH, or poor previous responses?
A clinic that concentrates on prognosis-favourable cases and declines or discourages challenging ones will naturally post higher pooled numbers. That does not mean their outcomes are better for a given patient type — it means their denominator is skewed toward easier cases.
This is not an implication that any specific clinic falsifies its figures — it is simply how statistics work when populations are not equivalent. The only honest comparison is same patient type against same patient type, ideally within age bands, ideally published to an independent national registry.
What is small-sample noise — and when should you be sceptical?
A clinic reporting a 75% success rate based on 40 transfers in a single year occupies a very wide statistical confidence interval. The true underlying rate could plausibly be anywhere from 60% to 87% — the uncertainty is large because the sample is small.
Large national registries aggregate thousands of cycles per year and can therefore publish figures with narrow confidence intervals. Individual clinic data, especially for smaller centres or for narrow subgroups (such as a specific age band with a specific protocol), can fluctuate substantially from year to year through chance alone, with no change in actual clinical quality.
Published data from international registries illustrates this clearly: year-on-year variation in individual clinic figures, even for well-performing centres, is routinely explained by sample-size variation rather than any change in practice.
When reviewing any clinic's published figures, ask: over how many transfers? Over what time period? A three-year figure of 300 transfers is a much more stable estimate than a single-year figure of 50.
What checklist of questions should you ask before trusting any success-rate claim?
The following questions apply to any success-rate figure you encounter — whether it is in a clinic brochure, on a website, in a consultation, or on a comparison platform:
- Which denominator? Per cycle started, per egg retrieval, or per embryo transfer?
- What is the definition of success? Positive pregnancy test, clinical pregnancy, ongoing pregnancy, or live birth?
- Is it age-banded? If not, ask for the figure specific to your age group.
- Fresh or frozen transfers, or combined? In what proportion?
- Per transfer or cumulative? If cumulative, over what time window?
- What is the sample size? How many transfers is this based on, and over how many years?
- Is it submitted to an independent registry? Or is it self-reported with no external audit?
- What is the patient mix? Does the clinic see patients with poor prognosis, multiple prior failures, or complex diagnoses?
- What time period does it cover? Technology and protocols change; figures from five years ago may not reflect current practice.
- Is the full methodology available in writing? An auditable methodology, not just a headline, is the mark of a transparent, trustworthy source.
No clinic — including Aansh — should expect you to simply accept a quoted figure without these questions. A clinic that is willing to answer all ten is demonstrating the transparency that is the actual basis for informed decision-making. A clinic that deflects or cannot answer them is not.
If you are considering IVF and want to discuss your individual situation and realistic age-appropriate expectations, our free second opinion is a good starting point. You can also review the choosing an IVF center guide for a structured framework, or read the full IVF treatment overview at Aansh.