Why PGT-M Is Built Around One Family, Not a Standard Test

Most fertility tests are ordered from a standard menu. PGT-M is not one of them. It is built around a specific inherited condition that has been identified in your family, and the laboratory has to construct a bespoke test before it can examine any embryo. That is why the preparation phase can feel slower and more document-heavy than other parts of IVF planning.

The short answer: PGT-M needs a confirmed known variant, a reliable source document describing it, and often DNA from family members so the laboratory can tell which embryo inherited which version of the gene. Each of those steps can add time, and some of them depend on relatives who may live in another country.

What PGT-M is actually testing for

PGT-M refers to preimplantation genetic testing for monogenic disorders — conditions linked to a change in a single gene. It is distinct from PGT-SR, which looks at chromosomal structural rearrangements, and from PGT-A, which assesses chromosome number. These tests answer different questions, and a treating team with a genetic counsellor should discuss which one fits a particular history.

Because PGT-M is aimed at a known condition rather than a general screen, the laboratory cannot simply run a universal panel. It has to know exactly what it is looking for in your family.

Step one: a confirmed variant and its paperwork

The starting point is usually a clinical genetic report — from you, your partner, an affected child, or another relative — that names the specific variant involved. The laboratory needs that documented variant, not a general description such as “a muscle condition runs in the family.”

This is where international patients often lose time. Reports may be old, written in another language, held by a relative, or never formally issued. Before anything else, it helps to locate the original report and check that it clearly identifies the gene and the variant. If no report exists, a diagnostic genetic work-up may be needed first, and that can add weeks before PGT-M planning can even begin.

If the report is missing or unclear

Ask the clinical team what documentation they would accept and whether a new genetic evaluation is required. This is a clinical question for the treating team and genetic counsellor, not something a coordination service can determine. What coordination can do is help you gather and organise the records you already hold so the clinical conversation starts with the right material.

Step two: why family samples are requested

A genetic report tells the laboratory what variant to look for. Family samples help it interpret what it finds in an embryo. In many PGT-M workflows, DNA from the parents — and sometimes from an affected child or other relative — is requested to establish which genetic markers travel with the variant. This is often described as phasing or linkage analysis.

The practical reason is that a single spot-check on a tiny embryo biopsy can be misleading. By tracking nearby markers across family members, the laboratory gains a second line of evidence about whether an embryo carries the familial variant. Family samples can also help identify situations where one version of the gene fails to amplify reliably — sometimes called allele dropout — which could otherwise produce a false result.

Which relatives are needed, and whether they are needed at all, depends on the condition and the laboratory’s design. That is a question for the clinical and laboratory team, and it is worth asking early because recruiting a relative for a blood or saliva sample can take weeks and may involve international shipping.

Step three: a custom assay must be designed and validated

Once the variant and family samples are in hand, the laboratory designs a test specific to your family and checks that it works before it is used on embryos. This design-and-validation stage is a major reason PGT-M planning has a longer runway than a standard IVF cycle. It cannot be compressed by booking flights earlier.

For international patients, the sequencing matters: the laboratory work generally needs to be complete before the IVF cycle reaches the point where embryos could be biopsied. Ask the clinic to explain, in writing, which steps must happen before you travel and which can happen while you are in Thailand.

What this means for your timeline and travel

Rather than treating PGT-M as a box to tick during a consultation, it helps to plan it as a project with dependencies. A useful way to think about it:

• Records first. Locate the genetic report and any family reports, and confirm what format and language the clinic accepts.
• Samples second. Confirm which family members need to provide samples, what type of sample, and how it should reach the laboratory.
• Design and validation third. Ask how long the laboratory expects this to take and what could delay it.
• Cycle planning last. Only then discuss dates, travel and medication planning with the clinical team.

This order matters because a travel date set before the laboratory work is confirmed can create pressure to rush steps that should not be rushed.

A worked planning example

Consider a couple living outside Thailand where one partner has a known familial condition documented in a report from several years ago. A sibling in a third country carries the same variant and is willing to help. A realistic preparation sequence might look like this: request the original report and a translated summary; ask the clinic which relatives’ samples would be useful and in what form; arrange the sibling’s sample collection locally and confirm shipping requirements with the laboratory; wait for the clinic to confirm the assay is ready; and only then agree a treatment calendar. Each hand-off involves a different person, which is why a written checklist with named responsibilities is more useful than a verbal plan.

Organising the paperwork from abroad

International PGT-M preparation is largely a records and communication task. A dated checklist helps: which report you hold, which relative holds another, which documents have been sent, and which questions are still open. If you would like a structured starting point, see the guide to preparing records for PGT-M genetic counselling and the companion article on organising PGT-M records as an international patient.

It also helps to understand where PGT-M sits among the available tests before you commit to a plan; the differences between PGT-A, PGT-M and PGT-SR are explained separately. If cost is part of your decision, comparing PGT-M costs across Thai hospitals covers what to check in a quotation, including whether laboratory design work is itemised.

Coordination support can help with the non-clinical side: organising existing records, drafting document requests to the hospital, coordinating a remote consultation, and planning travel around confirmed appointments. Clinicians and genetic counsellors interpret results, decide which samples are needed and advise on your individual situation. A coordinator does not diagnose, prescribe or confirm eligibility.

Questions worth putting to the clinical team

These are clinical and laboratory questions, and it is appropriate to ask them directly:

• Which genetic report do you need, and in what format?
• Which family members should provide samples, and what type of sample?
• How long does assay design and validation usually take for a variant like ours?
• What happens if a family sample cannot be obtained?
• Which steps must be finished before we travel?

Getting clear answers to these early is the most reliable way to avoid discovering a missing document or an unavailable relative halfway through planning.

Frequently asked questions

Can PGT-M go ahead if no one in the family has had genetic testing?

Sometimes a diagnostic genetic evaluation is needed first to identify the variant, which can add time before PGT-M planning begins. The treating team and genetic counsellor would advise on whether testing is appropriate and what it would involve.

Do both parents always need to provide samples for PGT-M?

Not necessarily. Which samples are requested depends on the condition, the laboratory's test design and the family history. This is a question for the clinical and laboratory team, and it is worth asking early because sample collection and shipping can take time.