Preimplantation Genetic Testing (PGT) is a significant advancement in fertility treatment, screening embryos for chromosomal abnormalities or specific genetic disorders during the In Vitro Fertilization (IVF) process. This screening identifies the healthiest embryos, enhancing the chances of a successful pregnancy and reducing the risk of miscarriage. PGT is a common step for many undergoing IVF.
Embryo Biopsy and Freezing
The initial phase of PGT involves embryo biopsy. This occurs when the embryo reaches the blastocyst stage, five to six days after fertilization. During the biopsy, an embryologist removes a small number of cells from the trophectoderm, the outer layer that forms the placenta.
Following the biopsy, embryos are almost always cryopreserved. This freezing allows time for genetic analysis by a specialized laboratory. It also provides a window for the patient to prepare for a subsequent frozen embryo transfer (FET) cycle, as a fresh transfer is not feasible while awaiting results.
Waiting for PGT Results
After biopsy, cells are sent to a specialized genetics laboratory for analysis. The lab examines the chromosomal content or specific genes. PGT results typically arrive within one to two weeks, though this can vary based on lab capacity and testing complexity.
Results classify embryos as euploid (normal chromosomes), aneuploid (abnormal number), or mosaic (mix of normal and abnormal cells). The medical team reviews these results, often with a genetic counselor, to determine which embryos are suitable for transfer. An embryo transfer cannot proceed until these results are obtained and evaluated.
Key Factors for Transfer Timing
After PGT results, several factors influence the timing of a frozen embryo transfer (FET). Clinic-specific protocols and scheduling play a role, as lab capacity and doctor availability must align with patient readiness.
Patient-specific biological factors are also important. The uterine lining must be adequately prepared to be receptive to an embryo, requiring careful timing with the menstrual cycle. A separate FET cycle is initiated to optimize the uterine environment. Some patients may undergo a “mock cycle” or follow specific medication protocols to ensure their uterine lining is ready for implantation.
Preparing for Transfer
The preparatory phase for an embryo transfer involves specific medical steps to optimize the uterine environment. Patients typically begin a medication protocol with estrogen to thicken the uterine lining. This thickening creates a supportive environment for the embryo.
Following estrogen therapy, progesterone is introduced. This hormone prepares the uterine lining for implantation. Regular monitoring, including ultrasounds and blood tests, ensures the uterine lining reaches optimal thickness and hormone levels are appropriate. This preparatory phase typically adds a few weeks between receiving PGT results and the actual embryo transfer.