INTEGRIS Bennett Fertility

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3433 NW 56th
Bldg. B, Suite 200
Oklahoma City, OK 73112

Pre-Implantation Genetic Screening and Diagnosis

Pre-implantation genetic testing (PGT) is a procedure performed in the laboratory during an IVF cycle in order to detect abnormalities in the chromosomes of the embryos or to test the embryo before it implants for a specific, known genetic disorder, usually caused by a single gene abnormality. An example of a chromosome abnormality is the presence of an extra chromosome 18 (Trisomy 18), which may lead to severe birth defects and death, usually before birth. An example of a known genetic disorder caused by single-gene defect is cystic fibrosis (CF), a disease leading to severe lung disease and shortened life span.

PGT involves removal of a cell or several cells from the embryo that has been formed in the laboratory from the union of sperm and egg during the IVF process. Under the microscope, the laboratory technician performs a biopsy of a day 5 or 6 embryo (blastocyst), and the cells that are removed are sent for genetic analysis at a special genetics laboratory off-site. The embryos are then frozen and stored (cryopreserved) in the IVF laboratory. Once the results are available, only genetically healthy embryos will be transferred into the uterus in the future.

The procedure of embryo biopsy involves special needles that are used under the microscope to gently separate cells, commonly from a day 5-6 embryo (blastocyst), from the trophectoderm, a part of the embryo that eventually will become the placenta. 

INDICATIONS FOR PRE-IMPLANTATION GENETIC TESTING (PGT)

Patients undergoing IVF

  1. Age 35 or older 
  2. With history of two or more consecutive miscarriages
  3. History of two or more failed IVF procedures (fresh or frozen embryo transfers)
  4. Male partner with severe male factor infertility
  5. Known genetic disorders carried by or affecting one or more parents. Such abnormalities are usually due to single gene defects. 

BENEFITS OF PGT:

The goal of pre-implantation testing (PGS/PGD) is to reduce the likelihood of conceiving a child with severe disease or to reduce miscarriages. It may also increase the chance of pregnancy in the case of couples with advanced maternal age, recurrent pregnancy loss, or repeated IVF failures.

Risks of PGT

As with any laboratory technique, accuracy of diagnosis may not be guaranteed. Misdiagnosis is still possible with PGT. Pregnancies with an abnormal child or a miscarriage or tubal (ectopic) pregnancies are still possible, as they naturally occur in non-IVF conceptions. Therefore, it is still recommended to pursue prenatal diagnosis after establishment of pregnancy following PGT as per guidelines for any pregnant woman.

PGT may result in damage to the embryo or may lower the implantation potential of the embryo. This is less likely if the embryo biopsied is at the blastocyst stage.

Freezing and thawing process of our embryos may result in damage to the embryos and reduction in the chance of pregnancy. The freezing and thawing process, however, does not increase the probability of having an abnormal child.

PGT techniques are not foolproof and may produce, in a small percentage of cases, normal results while the embryo is actually abnormal. In that case, the baby may be abnormal or a miscarriage may occur. In a small percentage of cases, the embryo may be normal but the PGT results abnormal, leading to denial of transfer of healthy embryos into the uterus. In some cases, all embryos may be abnormal by PGT, in which case no embryos will be transferred into the uterus unless the abnormality is minor in nature.

PGT techniques are a recent development and that there may be risks involved in this process that have not yet been identified.