For many people navigating fertility treatment, one of the most meaningful questions is whether a future child will be healthy. Preimplantation genetic testing (PGT) is a scientific tool that can help answer part of that question by analyzing embryos for chromosomal and genetic abnormalities before they are transferred to the uterus.
Understanding PGT begins with recognizing that it does not stand alone. It is performed as part of an in vitro fertilization (IVF) cycle, and the results it provides are one piece of a broader, personalized clinical picture. The decision to pursue preimplantation genetic testing (PGT) is made collaboratively between patients and their reproductive specialists, based on medical history, individual risk factors, and personal values.
This beginner's guide to preimplantation genetic testing explains what the process involves, who it may benefit, and what patients can realistically expect from it.
Preimplantation genetic testing is a diagnostic procedure used during IVF to examine embryos for specific genetic or chromosomal conditions before implantation. Rather than testing a pregnancy after conception, PGT allows clinicians to assess embryos in the laboratory at a very early stage of development, typically when they have reached the blastocyst stage at around five to six days after fertilization.
The goal is to provide clinicians and patients with more information about which embryos are most likely to result in a healthy pregnancy. It is important to understand that PGT does not guarantee a successful pregnancy or a child free from all health conditions. What it offers is a more informed starting point for embryo selection.
There are several distinct types of preimplantation genetic testing, each designed to detect different categories of genetic concerns. These are covered in detail later in this guide.
PGT is not a standard recommendation for every IVF patient. Clinicians typically discuss it in the context of specific medical histories or reproductive circumstances. Patients who may particularly benefit include:
It is also worth noting that carriers of genetic conditions may not always be aware of their status. Preconception or pre-cycle carrier screening, which is a separate process from PGT itself, can identify whether individuals carry variants associated with conditions such as cystic fibrosis, spinal muscular atrophy, or fragile X syndrome. This information can then inform whether PGT-M (monogenic testing) would be appropriate.
Preimplantation genetic testing is carried out within a standard IVF protocol. The process unfolds in several coordinated stages:
The patient undergoes ovarian stimulation using hormonal medications, which encourages the development of multiple follicles. Eggs are then retrieved in a minor outpatient procedure under sedation.
Retrieved eggs are fertilized in the laboratory using a partner's or donor's sperm, typically via intracytoplasmic sperm injection (ICSI). Resulting embryos are cultured over several days and monitored for development.
Once embryos reach the blastocyst stage, a small number of cells are removed from the trophectoderm, which is the outer layer of the embryo that eventually develops into the placenta. This biopsy is performed by an experienced embryologist and is generally considered to carry a low risk of damage to the embryo when carried out by a skilled team. The inner cell mass, which forms the fetus itself, is not disturbed.
Following biopsy, embryos are cryopreserved (frozen) while the extracted cells are sent to a genetics laboratory for analysis. This pause allows time for accurate testing without requiring an immediate fresh transfer.
The biopsied cells undergo genetic analysis in a specialized external laboratory. Depending on the type of PGT being performed, this may involve examining the number and structure of chromosomes, or testing for specific gene variants.
Results are returned to the treating fertility clinic and reviewed with the patient. Embryos identified as chromosomally normal or unaffected by a specific condition are prioritized for transfer in a subsequent frozen embryo transfer (FET) cycle. In cases where results are inconclusive, a clinician will discuss the available options.
There are three main categories of PGT, each with a different focus:
PGT-A (preimplantation genetic testing for aneuploidy) examines embryos for an abnormal number of chromosomes. Humans typically have 23 pairs of chromosomes, and deviations from this number (such as trisomies or monosomies) are associated with failed implantation, miscarriage, or conditions such as Down syndrome. PGT-A is the most commonly used form of preimplantation genetic testing in IVF.
PFCLA offers a detailed overview of PGT-A and related genetic screening services for patients who want to explore this in greater depth.
PGT-M (preimplantation genetic testing for monogenic or single-gene disorders) is used when one or both partners carry a known mutation associated with a specific inherited condition. Examples include BRCA gene mutations linked to hereditary breast and ovarian cancer, cystic fibrosis, sickle cell disease, and Huntington's disease. PGT-M is highly specific and requires advance laboratory preparation before the IVF cycle begins.
PGT-SR (preimplantation genetic testing for structural rearrangements) is designed for individuals who carry chromosomal rearrangements such as translocations or inversions. These structural variants can result in embryos with missing or extra chromosomal material, increasing the risk of miscarriage or developmental differences. PGT-SR identifies which embryos carry balanced or normal chromosomal arrangements.
One of the most important things to understand about PGT is that it is a highly sophisticated tool, but not a perfect one. Modern PGT platforms have a high degree of analytical sensitivity, but the possibility of false positive or false negative results exists, even in accredited laboratories.
A false positive result may indicate an abnormality in an embryo that is, in fact, viable. A false negative may miss a chromosomal issue that the test was designed to detect. These outcomes are uncommon, but they are part of the clinical reality that physicians discuss with patients before testing.
Another important phenomenon is mosaicism, where an embryo contains a mixture of chromosomally normal and abnormal cells. PGT-A may detect mosaicism, and the interpretation of mosaic results is an evolving area of reproductive medicine. Clinical guidance on transferring mosaic embryos varies between specialists and institutions, and patients should have detailed conversations with their care team about what mosaic results mean for their specific situation.
Reputable laboratories accredited by the College of American Pathologists (CAP) or certified through the Clinical Laboratory Improvement Amendments (CLIA) program adhere to rigorous quality standards. When evaluating fertility clinics, patients may find it useful to ask about the laboratory partnerships used for genetic analysis, the platform employed, and the quality assurance processes in place.
If all tested embryos are identified as chromosomally abnormal or affected by a specific genetic condition, the immediate path forward may feel uncertain.
In this situation, a fertility specialist would typically discuss several options. These may include:
No single answer is right for every person or couple. A clinical team will provide clear information and space for patients to process their results and make decisions that align with their values and circumstances.
Preimplantation genetic testing significantly reduces, but does not eliminate, the risk of chromosomal or genetic conditions in a resulting pregnancy. There are several reasons for this:
For this reason, patients who conceive following PGT are typically advised to continue with standard prenatal care, including any recommended prenatal genetic screening or diagnostic testing during pregnancy. PGT is a valuable tool that works best as part of a comprehensive, clinician-guided approach to reproductive care.
PGT adds to the overall cost of an IVF cycle, and this is an understandably significant consideration for many patients. The total cost depends on several factors, including the type of testing required, the number of embryos biopsied, the laboratory used, and the clinical fees associated with the biopsy procedure itself.
For a more detailed breakdown of what patients typically encounter when budgeting for genetic testing, this overview of PGT-A testing costs is a useful resource.
Insurance coverage for PGT varies considerably depending on the policy, state of residence, and clinical indication. Some insurers cover genetic testing when there is a documented medical necessity, such as a carrier status or history of genetic disease. In other cases, testing is an out-of-pocket expense. Fertility clinics often have financial counselors who can help patients navigate coverage questions and explore available financing options.
Pursuing preimplantation genetic testing is rarely a purely clinical decision. For many patients, the prospect of learning that embryos carry genetic abnormalities, or that no transferable embryos resulted from a cycle, is deeply distressing. The emotional weight of waiting for results, processing unexpected findings, and making decisions about embryo disposition can be considerable.
Patients are encouraged to seek psychological support throughout this process, whether through counseling services offered by the fertility clinic, independent mental health professionals specializing in reproductive health, or peer support communities. Fertility clinics with robust psychological support resources can be an important part of the care team.
It can also be helpful to understand, in advance, that results may include nuanced findings such as mosaicism, or that not every tested embryo will have a clear, actionable outcome. Discussing these possibilities with a clinician before testing begins can help patients feel more prepared, though it does not make the experience of receiving difficult results any less challenging.
For a balanced look at the benefits and trade-offs of genetic screening, this article on the pros and cons of PGS and PGT-A testing offers further context.
Preimplantation genetic testing is a sophisticated and meaningful option within reproductive medicine, and the decision to pursue it deserves thoughtful clinical guidance. Every patient's situation is different, and a personalized conversation with a fertility specialist is the most reliable way to understand whether PGT is appropriate, what type of testing may be most relevant, and what the realistic expectations are for a given set of circumstances.
Pacific Fertility Center Los Angeles has provided evidence-based fertility care to patients across a wide range of reproductive needs. If you have questions about genetic testing options, embryo selection, or any aspect of your fertility treatment, the PFCLA team is available to provide individualized guidance at every stage of the process.
To speak with a specialist or schedule a consultation, contact PFCLA directly. You do not have to navigate these decisions alone.