At a glance
Embryo biopsy for PGT is typically performed on day 5 or 6 of development, when a few cells are gently removed from the trophectoderm (future placenta) for genetic testing. The embryo is then frozen while results are analyzed.
What Is Embryo Biopsy for PGT?
Embryo biopsy is a step in preimplantation genetic testing (PGT) where a small number of cells are removed from an embryo to check for genetic or chromosomal conditions. In Thailand, this is almost always done on day 5 or 6 after fertilization, when the embryo has reached the blastocyst stage. The cells taken are from the trophectoderm, which will become the placenta, not the inner cell mass that forms the baby. This approach is considered safer than earlier biopsy methods.
Why Day 5 or 6?
By day 5 or 6, a healthy embryo has developed into a blastocyst with two distinct cell types: the inner cell mass (future baby) and the trophectoderm (future placenta). Biopsying the trophectoderm allows genetic testing without disturbing the cells that will become the fetus. Also, the embryo has more cells at this stage, so removing a few is less likely to affect development. Most IVF clinics in Thailand culture embryos to blastocyst before biopsy.
The Biopsy Procedure Step by Step
1. Embryo Selection
On the morning of day 5 or 6, the embryologist examines all embryos under a microscope. Those that have reached the blastocyst stage with a clear inner cell mass and trophectoderm are candidates for biopsy. Embryos that are still growing may be checked again on day 6.
2. Laser or Mechanical Opening
A small hole is made in the outer shell of the embryo (the zona pellucida) using a laser or a chemical solution. This allows the biopsy pipette to access the trophectoderm cells.
3. Cell Removal
A thin glass needle (pipette) gently suctions 3–5 trophectoderm cells from the embryo. The cells are carefully pulled away, often with the help of a laser to separate them. The entire process takes only a few minutes per embryo.
4. Embryo Freezing (Vitrification)
Immediately after biopsy, the embryo is frozen using a rapid cooling method called vitrification. This preserves the embryo while the biopsied cells are sent for genetic analysis. Freezing also allows time for test results before a frozen embryo transfer (FET) in a later cycle.
Is Embryo Biopsy Safe?
Trophectoderm biopsy is considered safe and is used worldwide. The removal of a few cells from the placenta-forming layer does not harm the inner cell mass. Studies show that the survival rate after thawing is high for biopsied embryos. However, as with any medical procedure, there are risks, including possible damage to the embryo or failure to survive freezing. Your clinic will discuss these risks with you.
What Happens After Biopsy?
The biopsied cells are sent to a genetics laboratory for analysis. Depending on the type of PGT (PGT-A for aneuploidy, PGT-M for monogenic disorders, or PGT-SR for structural rearrangements), results may take from a few days to several weeks. Meanwhile, your embryos remain frozen. Once results are ready, you and your doctor will discuss which embryos are suitable for transfer.
Questions to Ask Your Clinic
- What is your experience with trophectoderm biopsy?
- How many cells are typically removed?
- What is the survival rate after vitrification for biopsied embryos?
- How long does genetic testing take?
- Will the biopsy affect the timing of my embryo transfer?
Next Steps
- Confirm that your clinic performs day-5/6 trophectoderm biopsy.
- Ask about the genetic testing laboratory they work with and its accreditation.
- Discuss the costs of biopsy, freezing, and genetic analysis.
- Plan for a frozen embryo transfer in a subsequent cycle after results.
Frequently asked questions
Does embryo biopsy hurt the embryo?
The embryo does not have nerves, so it does not feel pain. The biopsy removes only a few cells from the trophectoderm, which is the part that becomes the placenta. Most embryos tolerate the procedure well.
How long does the biopsy procedure take?
The actual biopsy for each embryo takes only a few minutes. However, the overall process including embryo selection and preparation may take a couple of hours for all embryos.
Can the embryo be transferred fresh after biopsy?
In most cases, embryos are frozen after biopsy because genetic testing takes time. A fresh transfer is rarely done because the results are not available immediately. Frozen embryo transfer is the standard approach.
What is the success rate after biopsy and freezing?
Success rates vary by clinic and individual factors. Trophectoderm biopsy and vitrification have high survival and pregnancy rates, but you should ask your clinic for their specific data.
Are there any risks to the baby from embryo biopsy?
Current evidence suggests that trophectoderm biopsy does not increase the risk of birth defects or developmental problems. However, long-term studies are ongoing. Discuss any concerns with your doctor.
Continue your research
Medical information notice: This article is educational and does not replace individual assessment, diagnosis, genetic counselling or treatment advice from a licensed clinician. Provider services, availability, fees and policies should be verified directly before booking.
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