Preimplantation Genetic Testing for Aneuploidy (PGT-A), formerly known as PGS, is a procedure used in In Vitro Fertilization (IVF) to identify embryos with the correct number of chromosomes. This screening aims to improve the chances of a successful pregnancy by selecting embryos free of chromosomal abnormalities, which often cause implantation failure and miscarriage. The entire PGT-A process, from the initial embryo biopsy to the final report reaching the fertility clinic, typically takes between one to three weeks. The duration depends on the logistics of the fertility clinic and the efficiency of the genetics laboratory performing the analysis.
Preparing the Embryo for Testing
The PGT-A timeline begins at the fertility clinic after the eggs are fertilized and the embryos are cultured. Embryos must first reach the blastocyst stage, typically five or six days after egg retrieval. This stage is necessary because the embryo has differentiated into two distinct cell types: the inner cell mass (which becomes the fetus) and the trophectoderm (which forms the placenta).
An embryologist performs a biopsy by gently removing a small cluster of cells—usually five to ten—from the outer trophectoderm layer. This procedure is done without disturbing the inner cell mass. Once the biopsy is complete, the biopsied cells are placed into a transport tube, and the embryo is immediately cryopreserved (flash-frozen) via vitrification. Freezing the embryo is required because the genetic results are not available in time for a fresh embryo transfer. The extracted cell samples are then shipped to a specialized genetic testing laboratory.
Standard Laboratory Processing Time
Once the cell samples arrive at the genetics facility, the molecular analysis phase begins. Standard processing time for this laboratory work typically ranges from seven to fourteen days. The first step involves DNA extraction, isolating and purifying the tiny amount of genetic material from the biopsied cells.
Next, the DNA undergoes whole genome amplification (WGA) to create enough copies for accurate analysis. The amplified DNA is analyzed using advanced techniques, such as Next-Generation Sequencing (NGS) or array Comparative Genomic Hybridization (aCGH), to count all 23 pairs of chromosomes. Specialized software processes the sequencing data to detect aneuploidies (missing or extra chromosomes). Finally, a certified geneticist interprets the raw data and performs quality control checks before releasing the comprehensive report to the fertility clinic.
Variables That Can Alter the Schedule
While a two-week turnaround is common, several factors can accelerate or extend the time it takes to receive PGT-A results. Some laboratories offer “STAT” or urgent testing services, which can reduce the turnaround time to three to five days, though this often comes with a substantial additional fee.
The schedule can be altered by several variables:
- Batch processing: Many large-scale genetics labs wait to accumulate a minimum number of samples from multiple clinics before beginning the sequencing run.
- Logistical delays: Shipping issues involving holidays, weekends, or international transit can lengthen the timeline.
- Inconclusive results: If the initial biopsy sample contains too few cells or the DNA amplification fails, the lab may report an inconclusive result.
An inconclusive result necessitates a new biopsy, requiring the embryo to be thawed, re-biopsied, and refrozen. This process adds significant time to the overall schedule.
Integrating Results into the Treatment Plan
The PGT-A process concludes when the results are integrated into the patient’s treatment plan, adding a final phase to the timeline. The genetics laboratory delivers the results to the clinic’s medical team, who review the report and select the euploid (chromosomally normal) embryos. A consultation is then scheduled with the patient to discuss the results and finalize the embryo selection for transfer.
The next step is scheduling the Frozen Embryo Transfer (FET), which cannot occur immediately. The patient’s uterine lining must be prepared and synchronized to be receptive to the embryo. This involves a medicated cycle where the patient takes estrogen to thicken the endometrial lining, followed by progesterone for implantation readiness. This preparation phase generally takes several weeks, adding an additional month or two before the selected embryo can be thawed and transferred.