Embryology and Genetics Laboratories in PGT: Who Does What, and Where the Handoff Happens

A PGT result looks like a single line on a report, but it is the product of two laboratories doing different jobs at different times. The embryology laboratory grows the embryo, takes the sample and keeps the embryo safe while it waits. The genetics laboratory amplifies that sample and interprets what it finds. Most of the confusion patients experience — why a result is inconclusive, why a report has two voices, why a quotation seems to cover “PGT” but not everything — comes from not knowing where one laboratory’s responsibility ends and the other’s begins.

This guide walks through that relay step by step, then shows how to read a report and a quotation with the split in mind. It is general information, not a recommendation for your own case; questions about your embryos, your results and your options belong with the treating clinician and genetic counsellor.

Why one test needs two laboratories

PGT-A assesses chromosome number in cells sampled from an embryo, and testing has limitations and can produce incorrect findings (HFEA: PGT-A). The cells that get tested are not the embryo itself — they are a few cells removed from it. Everything before that removal is embryology; everything after it is genetics. The two teams rarely share a bench, sometimes do not share a building, and in some arrangements do not share a country.

That physical separation is normal and not a warning sign. What matters is that the handoff between them is controlled and documented.

The embryology side: from fertilisation to a labelled tube

The embryology laboratory’s PGT work begins well before any genetic question is asked.

1. Culture to blastocyst. The embryo is grown in the laboratory until it reaches a stage where a sample can be taken. The day this happens is recorded, because it becomes part of the embryo’s identity in later reports.
2. Biopsy. A small number of cells — typically from the trophectoderm, the outer layer that becomes the placenta rather than the baby — are removed. Biopsy is a real procedure with a real risk: HFEA patient information notes that embryo biopsy can cause damage and prevent further development (HFEA PGT-A FAQ). Ask your clinician what that risk means for your embryos specifically.
3. Washing, tubing and labelling. The sampled cells are washed, placed in a tube and labelled so they can be traced back to one embryo and no other. This is unglamorous work and it is where identity errors would occur if controls failed.
4. Vitrification of the biopsied embryo. The embryo is frozen while the sample travels. Its grade, biopsy day and freezing details are embryology observations — facts about the embryo, not conclusions about its chromosomes.

Notice what the embryology laboratory does not do: it does not decide whether the embryo is chromosomally normal. It produces a sample and a record.

The genetics side: from a few cells to a reported finding

The genetics laboratory receives a tube of cells, not an embryo, and must turn that into an interpretable result.

• Whole-genome amplification. A biopsy yields very little DNA, so it is copied many times over before analysis. This step is technically demanding and is one place where artefacts can enter.
• Platform and resolution. The laboratory chooses a testing method and a resolution — how small a change it will report. Different platforms and resolutions answer different questions, which is why “PGT” alone is not a complete description of a test.
• Matching the test to the question. PGT-A looks at chromosome number. PGT-M concerns a known monogenic condition, and PGT-SR concerns chromosomal structural rearrangements; these tests address different questions (HFEA: PGT-M and PGT-SR). PGT-M in particular usually requires preparatory work on the family’s genetic information before any embryo is tested, and that work sits on the genetics side.
• Interpretation against the embryo’s reported data. The genetics team reads its findings alongside the embryology record — which embryo, which day, what was observed. A result is only meaningful when it is attached to the right embryo.
• Reporting language. Reports use terms such as euploid, aneuploid, mosaic and inconclusive. Mosaic findings deserve particular care: a mosaic PGT-A result is inferred from intermediate chromosome copy-number findings in a biopsy sample, technical factors can contribute to such findings, and a sampled result does not establish the cell composition of the whole embryo (ASRM: mosaic PGT-A results). What a given report means for a transfer decision is a conversation with your clinician and genetic counsellor.
• Quality assessment. Laboratories run internal and external quality checks. Whether these exist, and what they cover, is a fair question to ask before treatment.

Where responsibility changes hands

The interesting part of this split is the seams. Four handoff points are worth understanding:

Handoff	What should be controlled	Why it matters to you
Sample identity	Labelling from biopsy through to report, with witnessing	A result must belong to your embryo and no other
Transport conditions	How the sample travels, packaging, temperature, timing, documentation	Degraded or mishandled samples can produce uninformative results
Re-biopsy decision	Who decides, on what basis, and what the embryo’s status is	Re-biopsy is a clinical decision with its own risks, not a routine repeat
Re-analysis decision	Whether the stored sample can be retested and who authorises it	Sometimes the sample, not the embryo, is the limiting factor

An inconclusive result can originate on either side. The sample may have been too small or degraded (embryology and transport), or the amplification and analysis may not have produced a clear signal (genetics). A report that simply says “inconclusive” without indicating where the uncertainty arose is harder to act on. Ask your clinician whether the laboratory has explained the likely source.

Reading a report that separates the two voices

A well-structured report reads in two registers. The embryology section describes observations: embryo identifier, biopsy day, grade, freezing details. The genetics section states the finding, the platform, the resolution and any limitations. Keep the two apart in your mind. An embryology observation is not a genetic conclusion, and a genetic result does not describe embryo quality.

If you are preparing for a consultation, it helps to bring the full report rather than a summary line, and to note which parts you want explained. If you would like help organising records and framing those questions before an appointment, the coordination service can assist with that practical preparation; interpretation of your results stays with your clinicians.

Comparing quotations when two laboratories are involved

Because the work is split, a quotation can be split too — and gaps hide at the seams. When you compare written quotations, check which laboratory performs which step rather than which provider sounds more impressive:

• Is the biopsy included, and is it priced per embryo or per cycle?
• Is the genetic analysis included for the number of embryos you realistically expect, and what happens to the price if more are biopsied?
• Is transport to an external genetics laboratory included, and who arranges it?
• Are re-analysis or re-biopsy charged separately?
• Is genetic counselling before and after testing included?
• Which laboratory issues the final report, and in what language?

Our guide to comparing PGT IVF quotes in Thailand sets out a fuller checklist, and a separate article explains how to verify a hospital’s laboratory pathway for PGT. If you want to understand how accreditation claims are checked, see confirming accreditation scope at a Bangkok provider. For readers still mapping out provider options more broadly, a countrywide comparison of IVF hospitals and clinics is available as background reading; it is a research starting point, not a statement about outcomes.

A worked planning example

Suppose a couple is preparing for PGT-M after a known familial condition has been identified. Their preparation list might look like this: the genetics laboratory’s preparatory work on the family’s genetic information (genetics side, often weeks before stimulation); the embryology laboratory’s culture and biopsy plan, including how many embryos they are prepared to biopsy; the transport arrangement if the two laboratories are in different places; and the report format they will receive. None of these steps tells them whether PGT-M is right for them — that is a clinical and genetic-counselling discussion — but knowing the sequence means they can ask specific questions at each stage instead of discovering a gap later.

PGT is not a guarantee of a successful pregnancy or a healthy child, and it is not necessary for every patient; whether to use it should be discussed for the individual situation (HFEA: PGT-A). Understanding the two-laboratory structure will not change that, but it will help you ask better questions of the people who can.

Frequently asked questions

If my PGT result is inconclusive, which laboratory is responsible?

It can be either. An inconclusive result may reflect the sample itself — too few cells, degradation during handling or transport — or the amplification and analysis stage. Ask your clinician whether the laboratory has identified the likely source, and whether re-analysis of the stored sample is possible before considering anything further.

Does the embryology laboratory decide whether an embryo is suitable for transfer?

No. The embryology laboratory records observations such as biopsy day and embryo grade, and the genetics laboratory reports a finding from the sample. How those pieces combine into a transfer decision is a clinical judgement made with you by your treating team.