How accurate is PGT-A testing?

PGT-A can identify chromosome-number differences in the sampled cells, but it is a screening test rather than a diagnosis of the whole embryo. Results can help an IVF team decide which embryo to consider for transfer, yet false-positive, false-negative, mosaic and inconclusive findings remain possible.

During PGT-A, a laboratory examines DNA from a small biopsy taken from the embryo's outer cell layer, which mainly develops into the placenta. Those cells may not have exactly the same chromosome pattern as cells elsewhere in the embryo. This sampling issue is one reason a result cannot describe every cell with certainty.

An euploid result means the tested sample showed the expected chromosome number; an aneuploid result means the sample showed a chromosome-number difference. A mosaic result suggests that the sample contained more than one cell pattern. An inconclusive result means the laboratory could not make a clear interpretation, sometimes because the DNA signal was limited or did not meet quality checks.

Review the full laboratory report with your fertility specialist rather than relying only on the result label. Ask which chromosomes were assessed, how the laboratory defines mosaic findings, whether embryo appearance and your treatment history also affect transfer decisions, and whether retesting would require another biopsy.

If pregnancy occurs after transfer, routine prenatal care still matters. PGT-A does not check every genetic condition, developmental problem or pregnancy complication. Your obstetric clinician can explain prenatal screening and diagnostic options in the context of the transferred embryo's report and your preferences.

Arrange a discussion before making an embryo-transfer decision if the report is mosaic, inconclusive or different from what you expected. Promptly contact your fertility clinic for heavy bleeding, severe or worsening pelvic pain, fainting, breathing difficulty or fever during treatment or early pregnancy; these symptoms need assessment regardless of the PGT-A result.

Useful questions include: What does this laboratory's wording mean for my embryo? Could sampling or mosaicism change the interpretation? What are the possible benefits and drawbacks of transfer, storage, another biopsy or not using this embryo? Which prenatal tests would be relevant if a transfer leads to pregnancy? A genetic counsellor can help you consider uncertain or mosaic findings before you decide.