A significant share of first-trimester miscarriages trace back to chromosomal errors in the embryo rather than to anything either parent did. That single fact is why PGT-A testing in IVF has become a common point of discussion for couples who have faced pregnancy loss or repeated IVF setbacks. Understanding what the test screens for and what it cannot control helps set realistic expectations before a cycle begins.
What Is Preimplantation Genetic Testing (PGT-A)?
Preimplantation Genetic Testing for Aneuploidy, shortened to PGT-A, checks whether an embryo carries the correct number of chromosomes. A typical human embryo has 46 chromosomes. When an embryo has extra or missing chromosomes, a condition called aneuploidy, it is far less likely to implant and more likely to end in miscarriage. During an IVF cycle, embryos are grown in the laboratory to the blastocyst stage, usually on Day 5, 6, or 7. A few cells are then taken from the outer layer that later forms the placenta, and those cells are analyzed in a genetics laboratory.
How IVF Genetic Screening Selects Healthy Embryos
IVF genetic screening for healthy embryos follows a set sequence. Once embryos reach the blastocyst stage, an embryologist performs a small biopsy on each one. The embryos are frozen while the sample is sent for analysis. When results return, embryos are grouped as euploid, meaning the expected chromosome count, or aneuploid. A euploid embryo is then chosen for a frozen embryo transfer in a later cycle. In this context, a healthy embryo means one that is chromosomally normal. It does not guarantee a healthy baby in every respect, because PGT-A looks only at chromosome number, not at every genetic or developmental factor.
Can PGT-A Prevent Miscarriage?
Because chromosomal abnormalities are among the most common causes of early pregnancy loss, transferring a chromosomally normal embryo can lower the risk of a miscarriage driven by those errors. This is the core reason the test is offered. However, PGT-A does not eliminate all risks. Miscarriages can also result from uterine conditions, hormonal imbalances, immunological factors, and other causes that a chromosome screen does not detect. A more accurate way to describe it is that PGT-A may reduce the likelihood of miscarriage linked to aneuploidy, but it cannot rule miscarriage out completely. A fertility specialist can explain how relevant the test is for a specific diagnosis.
Genetic Testing Before IVF: Who May Benefit
Genetic testing before IVF is not recommended for every patient. It tends to be most relevant for women of advanced maternal age, since the proportion of aneuploid eggs rises as a woman gets older. It is also considered for couples who have experienced recurrent pregnancy loss, repeated implantation failure across previous IVF cycles, or a known chromosomal rearrangement in one partner. When a partner carries a known structural rearrangement (like a balanced translocation), a specialized test called PGT-SR is used alongside PGT-A. A related test, PGT-M, is used when there is a family history of a specific inherited single-gene condition.
Benefits of PGT-A in IVF
The benefits of PGT-A in IVF center on making the embryo transfer more informed. By identifying which embryos are chromosomally normal, the team can prioritize the embryo most likely to implant, which may reduce the number of failed transfers along with the repeated cost and emotional strain that come with them. Screening also supports single embryo transfer, lowering the chance of a twin or higher-order pregnancy and the risks that follow.
| What PGT-A Can Do | What PGT-A Cannot Do |
| Identify chromosomally normal (euploid) embryos | Guarantee a pregnancy or a live birth |
| Lower the risk of miscarriage caused by aneuploidy | Prevent miscarriage from nonchromosomal causes |
| Support single-embryo transfer | Correct or repair an abnormal embryo |
| Reduce repeated failed transfers for suitable patients | Screen for every genetic or single-gene condition |
The test does add cost and time, requires embryos that reach the blastocyst stage, and can occasionally return mosaic results, meaning the biopsy shows a mixture of both euploid and aneuploid cells, which requires tailored genetic counseling to interpret. For these reasons, it remains a shared decision between the couple and the specialist.
Frequently Asked Questions
No. PGT-A screens for the overall number of chromosomes in an embryo. PGT-M tests for a specific inherited single-gene condition when there is a known family history. PGT-SR checks for changes in chromosome structure when a parent has a known chromosomal change, such as a translocation.
No. It confirms that an embryo has the expected chromosome count, which is only one part of a healthy pregnancy.
When performed by experienced embryologists at the blastocyst stage, the biopsy is generally considered safe and does not harm the inner cell mass that forms the fetus. The treating team can explain the process in detail during a consultation.
Talk to a Specialist
Couples considering genetic testing as part of IVF benefit most from a case-specific discussion. To learn whether PGT-A or PGT-M suits a particular diagnosis and treatment plan, book a consultation with the specialists at 9M Fertility.
