IVF success rate measures explained: retrievals, transfers and cumulative rates
A plain-English glossary of every measure on a CDC clinic report, and which ones matter most for your decision.
CDC's clinic reports contain more than twenty different measures. They are not interchangeable: each answers a different question and uses a different denominator. This guide explains each measure shown on our clinic pages, in the order they appear, using CDC's own definitions and the 2022 national figures from CDC's data.
The building blocks
ART cycle. CDC counts a cycle from the day a patient starts medication or monitoring with the intent to have an egg retrieval or an embryo transfer. A cycle may end at any step — before retrieval, after retrieval with no embryo to transfer, or with a transfer.
Intended egg retrieval. A cycle started with the plan to collect eggs, whether or not eggs were actually collected. It includes cycles cancelled for poor response.
Actual egg retrieval. A cycle in which eggs were collected.
Transfer. A procedure in which one or more embryos are placed in the uterus. Transfers can use fresh embryos from the same cycle or frozen embryos from an earlier one.
Live-birth delivery. The birth of one or more live babies. Twins count as one delivery. That is why CDC reports both “deliveries” and “infants born” on the clinic profile.
Measures for new patients
New patients are those using their own eggs who had no previous ART cycle. For them CDC reports:
- Live birth after 1 intended egg retrieval — of new patients who started a first retrieval cycle, the share who had a live birth from that retrieval, counting all transfers of embryos made from it, fresh or frozen.
- Live birth after 1 or 2 intended retrievals — the same, allowing a second retrieval.
- Live birth after all intended retrievals — the cumulative share of new patients who had a live birth from any retrieval started in the reporting period.
- Average intended retrievals per new patient — how many retrieval cycles the clinic's new patients typically went through.
These patient-based, cumulative measures are the closest CDC comes to answering “what happened to people like me who started here?” Nationally in 2022, 60.8% of new patients under 35 had a live birth after all intended retrievals; for patients over 40 the figure was 13.4%.
Measures for all own-egg patients
This group includes patients who had previous ART cycles.
- Live births per intended egg retrieval — the share of all intended retrievals that led to a live birth. National 2022: 49.7% under 35, 36.3% at 35–37, 23.1% at 38–40, 7.7% over 40.
- Live births per transfer — the share of embryo transfers that led to a live birth. Because it leaves out cycles that never reached a transfer, it is always higher than the per-retrieval rate, especially for older patients. National 2022: 49.1% under 35 and 25.4% over 40.
- Single, term, normal-weight births per transfer — the share of transfers that produced one baby, born at 37 weeks or later, weighing at least 2,500 grams (about 5.5 lb). It is a measure of healthy outcomes, not just births.
- Average intended retrievals per live birth — how many retrieval cycles, on average, stood behind each live birth.
Measures for donor eggs and embryos
When the eggs come from a donor, the donor's age matters far more than the recipient's, so CDC reports donor results for all ages together, split by type: fresh embryos from fresh donor eggs, fresh embryos from frozen donor eggs, frozen embryos originally made from donor eggs, and donated embryos. Each is reported per transfer. Many clinics perform few donor transfers of a given type, so fractions and suppressed cells are common here. See our donor guide.
How to spot a flattering measure
Every measure is honest, but some are easier to look good on:
- Per-transfer rates reward clinics that cancel poor-prognosis cycles before transfer, because those cycles vanish from the denominator.
- Live-birth rates count twins as one success. Compare them with the single, term, normal-weight rate to see how much of a clinic's success relies on multiple births.
- All-patient rates move with the clinic's case mix. A referral centre for difficult cases will look worse here than it is.
Cumulative new-patient measures are the hardest to flatter, because they start counting from the first intended retrieval and follow every embryo.
Fractions, asterisks and blanks
CDC shows a fraction such as 4/15 when fewer than 20 cycles stand behind a rate. An asterisk replaces a count of 1 to 4 that CDC suppressed for privacy, and any value that would let a reader work out that count is suppressed too. “No cycles” means the clinic reported none in that group. We print all of these as CDC does, and we never convert a small fraction into a percentage.
The count under each table
Under each table we print CDC's count for the measure across all age groups — for example, the total number of intended retrievals behind the own-egg table. It tells you how much data the table rests on. A clinic with a few hundred cycles gives you far more stable figures than one with thirty.
Which measure should I focus on?
If you are new to IVF and plan to use your own eggs, start with live birth after all intended retrievals for your age group, then look at average intended retrievals per new patient to understand how many cycles that took. If you have had IVF before, the all-patient per-retrieval rate is more relevant. If you plan to use donor eggs, look at the donor table and the size of the numbers behind it. In every case, check the single, term, normal-weight rate and read CDC's guidance on interpreting success rates.