The timeline for preimplantation genetic testing (PGT) is highly variable, depending on multiple distinct phases beyond the time the sample spends in the genetics laboratory. PGT examines embryos created through in vitro fertilization (IVF) for chromosomal abnormalities (PGT-A), single-gene disorders (PGT-M), or structural rearrangements (PGT-SR). This testing is valuable for selecting the healthiest embryos for implantation, improving the chances of a successful pregnancy and reducing the risk of miscarriage. The full journey involves time for embryo development, analysis at an external facility, and preparation of the patient’s body.
Embryo Development and Biopsy Timeline
The first phase of the process occurs entirely within the fertility clinic’s laboratory following egg retrieval and fertilization. Embryos must grow for several days until they reach a sufficiently developed stage to allow for a safe biopsy. This crucial development period, from fertilization to the blastocyst stage, typically takes five to seven days.
The blastocyst stage is ideal for PGT because the embryo has differentiated into two main cell types: the inner cell mass, which will form the fetus, and the trophectoderm, which will form the placenta. A few cells are carefully removed from the trophectoderm layer, a procedure known as the embryo biopsy. Waiting until this stage ensures that the removal of cells does not compromise the development of the future fetus.
Biopsies are performed on Day 5, Day 6, or occasionally Day 7 of development, depending on when each individual embryo reaches the blastocyst stage. Once the cells are secured for testing, the embryos are immediately frozen using a technique called vitrification. Freezing is necessary because the embryo transfer cannot proceed until the PGT results are returned, which forces a delay to the next menstrual cycle. This initial stage, from fertilization to freezing, adds approximately one week to the overall timeline.
Genetics Laboratory Processing Duration
The standard turnaround time for the most common test, PGT-A (screening for an abnormal number of chromosomes), is seven to fourteen days from the genetics laboratory’s receipt of the biopsied sample. This duration includes time for quality control, DNA amplification, sequencing, and the interpretation of results by geneticists.
Factors influencing the turnaround time include the laboratory’s current workload, shipping distance, and the specific type of testing requested. Some laboratories offer an expedited service, which may return PGT-A results in five to seven days, though this option often comes with an increased cost. Weekends and holidays can also temporarily pause processing, contributing to the longer end of the expected range.
Testing for single-gene disorders (PGT-M) or chromosomal structural rearrangements (PGT-SR) requires a significantly longer duration. For PGT-M, the genetics lab must first custom-create a DNA probe specific to the family’s genetic mutation, which can take three to four weeks. This initial probe setup adds a substantial delay to the overall testing process for patients with known heritable conditions. Once the probe is ready, the analysis of the biopsied cells follows the standard seven-to-fourteen-day timeline.
Planning the Frozen Embryo Transfer
After the genetics laboratory sends the PGT results back to the fertility clinic, the final phase involves preparing the patient’s uterus for a frozen embryo transfer (FET). Even with the results in hand, the transfer is not immediate because the uterine lining must be synchronized to the exact developmental stage of the frozen embryo. This physiological preparation is orchestrated through a medicated cycle.
Preparation involves taking estrogen medication for two to three weeks to thicken the endometrial lining. This is monitored closely with ultrasound scans to ensure the lining reaches the appropriate thickness. Once the lining is ready, progesterone medication is introduced, signaling to the uterus that the body is ready for implantation.
The transfer is scheduled five or six days after progesterone is started, matching the timing of the embryo’s development. The entire preparation cycle, from the start of the menstrual cycle to the transfer, usually takes three to six weeks. This duration depends on the patient’s response to medication and the clinic’s scheduling, often making it the longest component of the overall timeline following the embryo biopsy.