Genetic testing results usually arrive as a PDF from a reference laboratory, sometimes weeks after your retrieval. They are often dense, full of chromosome shorthand, and sent before anyone has walked you through them. This guide takes the report apart section by section, so you can read your own and arrive at your follow-up appointment with the right questions. It is about reading the document. For whether to test in the first place, see What is PGT?
The parts of a typical report
| Section | What it contains | What to check |
|---|---|---|
| Patient and cycle details | Names, dates of birth, clinic, retrieval date, sometimes egg and sperm source | That the details are yours, and that donor gametes are recorded correctly |
| Test type | PGT-A (chromosome number), PGT-M (a specific inherited condition), PGT-SR (a structural rearrangement), or a combination | That the test you consented to is the one reported |
| Method or platform | The technology used, often next-generation sequencing, and sometimes its resolution or reporting thresholds | Note it. It matters for how mosaic and segmental results are defined |
| Embryo list | Embryo ID, day of biopsy, often the morphology grade at biopsy | That the IDs match your clinic's embryo storage records exactly |
| Result per embryo | The category, plus a chromosome-level summary | The category and any notes or caveats |
| Interpretation and limitations | The lab's standard wording on accuracy and what the test cannot detect | Read it. It is where the lab sets out the test's limits |
The result categories
Euploid
The expected number of chromosomes was detected in the biopsy sample. Euploid embryos are usually first in line for transfer, ranked by grade and day of development. Euploid does not mean guaranteed. Implantation and pregnancy still depend on many other factors.
Aneuploid
A whole extra chromosome or a missing one was detected. Reports usually show this with shorthand such as "+16" for an extra chromosome 16, or "−21" for a missing chromosome 21. Notation varies between labs. How reliable is an aneuploid call? ASRM's 2024 committee opinion notes that few studies report it directly. In one study it cites, 102 embryos reported aneuploid were transferred and none resulted in an ongoing pregnancy (ASRM, 2024).
Segmental
Part of a chromosome, rather than a whole one, appears gained or lost. Some labs report these separately. Others fold them into "aneuploid" or "mosaic." If you see a segmental finding, ask how your lab and clinic treat it, because policies differ.
Mosaic
The sample appeared to contain a mixture of cells with normal and abnormal chromosome counts. Here the lab's method matters most. ASRM explains that mosaicism is inferred from intermediate results, values between clearly normal and clearly abnormal. Those intermediate values can also reflect technical noise, amplification bias or contamination. How often a lab reports mosaicism depends on its platform and the thresholds it sets (ASRM, 2024). The HFEA notes that healthy births have been reported after mosaic embryo transfers, though possibly with a lower chance of pregnancy, and that clinics' handling of mosaic embryos varies (HFEA, 2023). Our mosaic embryos guide covers the decision in depth.
No result, or inconclusive
Sometimes the sample does not give a readable result. ASRM reports this happens in 0.86% to 3.8% of biopsies. The options are usually to transfer the embryo untested, or to warm, re-biopsy and refreeze it. ASRM describes the data on re-biopsy as mixed, with some studies showing lower pregnancy rates after a second round of biopsy and freezing.
Reading the chromosome summary
Many reports include a small chart or table for each embryo. It lists chromosomes 1 to 22 plus the sex chromosomes, and marks any that look abnormal. The sex chromosomes are part of the aneuploidy check, because extra or missing X or Y chromosomes are also chromosomal abnormalities. A clean summary with no flags normally matches a euploid call. Flags usually show which chromosome is affected, whether it is a gain or a loss, and whether it is whole or segmental. If the summary and the headline category do not seem to match, ask the lab or your genetic counsellor to explain.
PGT-M and PGT-SR results look different
If you are testing for a known inherited condition (PGT-M), the report gives a result for that condition, often written as "affected," "unaffected" or "carrier." PGT-SR reports address a known rearrangement, such as a translocation, in one partner. These tests are often run alongside PGT-A, so a single embryo may carry two results, for example "unaffected" for the condition and "aneuploid" for chromosome number. Read both before you rank embryos.
Accuracy: what the report cannot promise
The HFEA lists the main limits plainly: the test may miss an abnormality, or report one that is not there. Because the result comes from a few cells taken from the outer layer, it may not reflect the whole embryo. ASRM adds that testing platforms keep evolving, that no single platform has been shown to be clearly better, and that lab protocols and quality controls differ. None of this makes the report useless. It means each category is a probability statement from one sample, and your decisions should allow for that.
When the grade and the genetic result disagree
It is common to find that your best-looking embryo came back aneuploid, while a modest one is euploid. That is not a lab error. Grading describes how an embryo looks, and genetic testing describes its chromosome count from a small sample. The two measure different things. Where both are available, clinics usually put the genetic result first and then use the grade to order embryos within the same genetic category. Ask your clinic to explain its order if it is not obvious from the report.
Turn the report into an embryo inventory
Once you have the report, make your own one-page record and keep it with your clinic's storage paperwork. An illustrative layout:
| Embryo ID | Day biopsied | Grade | PGT result | Clinic status |
|---|---|---|---|---|
| E1 | 5 | 4AA | Euploid | Stored, first for transfer |
| E2 | 6 | 4BB | Mosaic (lab notes "low level") | Stored, pending counselling |
| E3 | 5 | 3BB | No result | Stored, re-biopsy option discussed |
| E4 | 6 | 4BC | Aneuploid (+16) | Per written disposition policy |
This is the document a new clinic will ask for if you move or ship embryos. It also makes transfer planning far less confusing. For what the grades mean, see embryo grading explained. If your embryos may need to move between countries, the IDs on this list and on the shipping paperwork must match exactly. Our guide to shipping frozen embryos internationally explains why.
Questions to ask at your results appointment
- Which platform did the lab use, and what thresholds does it use for mosaic and segmental results?
- Are segmental findings reported separately or grouped with other categories?
- What is the clinic's written policy for aneuploid, mosaic and no-result embryos? ASRM recommends that patients receive a written disposition policy.
- Would you transfer a mosaic or no-result embryo, and in what order?
- Can I talk to a genetic counsellor about any result I do not understand?
- Can I have the full report, not just a summary, for my records?
Scope note: this guide covers reports for chromosome screening and for known inherited conditions only. Selecting embryos by sex or by non-medical traits is outside what this site discusses.
Frequently asked questions
How long does it take to get PGT results?
It depends on the lab and on shipping time from the clinic. Embryos are usually frozen after biopsy, so the results do not delay anything urgent. They are needed before you plan a frozen transfer.
Why does my report list a grade as well as a genetic result?
The grade records how the embryo looked when it was biopsied. Clinics usually use it to choose the order in which euploid embryos are transferred.
Can a euploid result be wrong?
Yes. The HFEA notes the test can miss abnormalities. The biopsy samples only a few outer cells, so a euploid result is a strong but not perfect indicator.
Should I destroy embryos reported as aneuploid?
That decision is yours, within your clinic's rules and local law. Ask for the written disposition policy and talk it through with a genetic counsellor before deciding.
Can I get the raw data from the genetics lab?
Some labs will share more detailed data on request through your clinic. It is worth asking if you are seeking a second opinion on a mosaic or segmental result.
Sources
The Takeaway
Read the platform, the categories and the limitations together, match every embryo ID to your storage records, and get the clinic's written policy for each category before you make transfer or disposition decisions.