Enter embryo grade and transfer day to estimate implantation and live birth chances for your context. See per-transfer ranges, odds after 1–3 transfers, and multiples risk if transferring two.
Methodology & Sources
What this estimates
The tool provides educational ranges for per-transfer implantation and the probability of at least one live birth across one to three transfers based on embryo day and grade, egg or embryo age, egg source, and PGT status. It also displays an estimated multiples risk when transferring two embryos. Figures are population-style summaries and not clinic-specific success rates.
How grading is mapped
- Blastocyst grading (Gardner): expansion digit 3 to 6, inner cell mass grade A to C, trophectoderm grade A to C. The calculator applies small multipliers for expansion and letter grades, with A higher than B, and B higher than C.
- Day-3 grading: cell count and a simple A to C morphology grade. Eight cells with grade A is treated as favourable. Fewer than 7 or more than 9 cells reduce the factor slightly.
Age and source
A baseline untested implantation chance is set from egg or embryo age, with lower values at older ages for own-egg cycles, and a higher baseline for typical donor ages. Day 6 blastocysts are given a small reduction relative to day 5, and day 3 transfers are reduced relative to blastocyst transfers.
PGT status and cycle type
- PGT euploid: implantation mapped higher than untested embryos.
- PGT aneuploid: implantation mapped near zero.
- ICSI vs IVF: a neutral to very small adjustment is used, since grade and age dominate outcomes.
From implantation to live birth
The tool converts implantation probability to a per-embryo live-birth probability using a constant factor that is higher for euploid embryos and lower for untested embryos. For single embryo transfer, the per-transfer live-birth chance equals the per-embryo value. For two embryos, it uses the complement rule, that is, 1 minus the probability that neither embryo leads to a live birth.
Cumulative probability across transfers
For two or three planned transfers with the same plan, the probability of at least one live birth is calculated as 1 minus the product of failure probabilities across transfers.
Multiples risk when transferring two
The estimate includes the chance that both embryos succeed in the same transfer and a small monozygotic component per implanted embryo. Single embryo transfer is shown with only a small monozygotic twin risk.
Bounds and presentation
Outputs are clamped to plausible ranges and shown as a centre value with a simple ± band to reflect typical variation between clinics and protocols. Clinic-reported rates may be higher or lower than these ranges.
Limits
- No adjustment for clinic-specific lab conditions, biopsy techniques, cryo method, stimulation protocol, or endometrial synchrony.
- No adjustment for uterine factors, recurrent loss, fibroids, or hydrosalpinx.
- Grading systems vary by clinic. Letter and expansion mappings are simplified.
- For day 3 transfers, fragmentation and symmetry are not explicitly modelled.
Sources
- HFEA, embryo grading overview (patient guidance on grading and what grades mean).
- CDC ART reports (US national outcomes by age and ART type).
- SART patient resources (clinic-level outcomes and elective single embryo transfer information).
- ASRM guidance on number of embryos to transfer (single embryo transfer preference and multiples risk).
- Gardner DK, Schoolcraft WB, blastocyst culture and transfer descriptions used widely in IVF programs.
- Published studies comparing day 5 and day 6 blastocyst outcomes and the impact of euploidy on implantation and live birth.
Educational use only, not medical advice. Discuss your clinic’s specific success rates and transfer plan with your fertility specialist.
What each input means
- Egg source: Own eggs or donor eggs. Egg age is taken from the source (donor’s age if donor eggs).
- Egg/embryo age: The age at retrieval that drives most of the estimate.
- Cycle type: IVF or ICSI. Used for labelling and context.
- PGT status: Untested, euploid, or aneuploid. Euploid is expected to have higher implantation; aneuploid is generally not transferred.
- Day of transfer: Day 3, Day 5, or Day 6.
- Embryo grade: Select your grade (e.g., 4AA, 5BB) or Day-3 cell count with grade.
- Number to transfer per attempt: One or two embryos per transfer attempt.
How to read the results
- Per-transfer implantation range: A range based on grade × egg age × transfer day and PGT status.
- Live-birth probability after n transfers: Chance of at least one live birth after 1–3 transfers with your chosen number per attempt.
- Multiples risk (if transferring two): An estimate of twins or higher order multiples risk when two embryos are transferred.
- Limits: Results use population averages. Clinic and lab outcomes vary. Many programs prefer single embryo transfer to reduce multiples.
This tool is educational only and cannot predict an individual outcome.
Frequently asked questions
What do blastocyst grades like 4AA or 5BB mean?
The first number is expansion (1–6). The first letter is inner cell mass quality. The second letter is trophectoderm quality.
Are Day-5 embryos better than Day-6?
Day-5 often shows higher implantation than Day-6 in population data, but lab and patient factors vary.
How does PGT change estimates?
Euploid embryos typically have higher implantation. Aneuploid embryos are usually not transferred in clinical practice.
Why does egg age matter with donor eggs?
Success tracks the age at retrieval. Donor cycles use the donor’s age for estimates.
Is transferring two embryos always better?
Transferring two can raise the chance per attempt but also increases multiples risk. Many clinics prefer single embryo transfer to limit that risk.