PGT — Preimplantation genetic testing

PGT (preimplantation genetic testing) is optional testing performed on embryos created during IVF, before transfer. A few cells are biopsied from each embryo at the blastocyst stage (day five or six) and sent to a specialized genetics lab. There are three types: PGT-A (chromosome screening), PGT-M (single-gene disorders), and PGT-SR (structural rearrangements).

PGT-A screens embryos for the correct number of chromosomes — the most common form of testing. PGT-M tests for a specific inherited genetic condition (like cystic fibrosis or Huntington's) when one or both parents are known carriers. PGT-SR looks for chromosomal structural rearrangements when a parent has a known translocation. Most patients who do PGT are doing PGT-A.

PGT-A can reduce miscarriage risk and shorten time to pregnancy by prioritizing chromosomally normal embryos, which is particularly valuable for patients over 35 or with recurrent pregnancy loss. PGT-M can prevent transmission of a specific serious genetic condition. What PGT does not do is create healthier embryos — it selects among the embryos you already have.

No. For patients under 35 producing many good embryos, the added cost and small biopsy risk may not be justified. For patients over 35, those with recurrent miscarriage, or those with failed prior transfers, PGT-A often makes sense. We give you an honest recommendation rather than defaulting to add-on testing for everyone.

Whether preimplantation genetic testing is covered depends on your plan and your indication. Coverage is more likely where there is a known genetic condition in the family or in either intended parent. Plans often distinguish between embryo biopsy for a specific inherited condition and elective testing — for chromosome counts generally, or for sex selection. We will work with your insurer to establish what your plan allows.

PGT-A is highly accurate for detecting whole-chromosome abnormalities, but no test is perfect. Mosaic embryos (embryos with a mix of normal and abnormal cells) can produce ambiguous results, and rare false negatives and false positives occur. Standard prenatal testing is still recommended in pregnancy even after PGT.

A mosaic embryo has a mix of chromosomally normal and abnormal cells in the biopsy sample. Some mosaic embryos self-correct and produce healthy babies; others do not. When only mosaic embryos are available for transfer, we discuss the specific type of mosaicism, current outcome data, and genetic counseling before you decide.

In experienced hands, embryo biopsy does not measurably harm implantation potential. The biopsy is performed by an embryologist on day five or six of development, when the embryo has hundreds of cells and the cells being removed will not contribute to the baby.

Yes — PGT-A necessarily identifies the sex chromosomes of each embryo. Whether that information is shared with you and whether it's used in embryo-selection decisions is your choice, and we discuss the ethical and family-planning implications before testing.

Results typically come back in one to two weeks. Because you cannot transfer an embryo the same cycle it's biopsied, PGT patients always plan on a frozen transfer in a later cycle.