Preimplantation Genetic Diagnosis (PGD) at WCFC
A Promising New Technology, PGD, or embryo screening, is now available to assist couples.
A few years ago, Pre-Implantation Genetic Screening (PGD) was introduced as a promising technique to assist couples who were diagnosed with transmissible genetic diseases such as Cystic Fibrosis, Muscular Dystrophy, Tay-Sachs, Down syndrome, and others.
Also known as embryo screening, PGD is an advanced procedure used in conjunction with in-vitro fertilization (IVF). The technique helps to prevent an adverse outcome by identifying abnormal embryos while they are developing in our laboratory but before they are transferred to the uterus.
At West Coast Fertility Centers, PGD has also been used to help patients unable to initiate or sustain a pregnancy. For our patients with a history of recurrent miscarriages, we can evaluate their embryos and implant those that have been normally screened thereby offering a better prospect for a healthy pregnancy. Genetic screening is important because during visual scoring of the embryos, those that are chromosomally abnormal may look no different than "normal" embryos. Therefore, embryo biopsy is very helpful when selecting healthy embryos to be transferred.
Who May Benefit From PGD?
Embryos that carry certain chromosomal or genetic conditions may fail to initiate implantation to the uterine lining. Other outcomes may be a pregnancy loss or the birth of a child with physical, mental, and learning disabilities. PGD is useful for patients who have other types of reproductive medical problems. Here are some examples of when PGD is recommended to our patients:
- Recurrent miscarriages (usually more than 2)
- Women 35 and older who produce 6 or more embryos with IVF
- Family history of chromosomal conditions or history of X-linked disease
- Unexplained infertility
- 2 or more unsuccessful cycles
It is well known that fertility in general decreases with maternal age. Research has confirmed that genetic abnormalities also increase with advancing maternal age. A major cause of low implantation is that many embryos are chromosomally abnormal and they seldom implant or get to deliver. PGD allows for the selection of the best quality embryos which are then transferred during IVF, therefore reducing the incidence of a chromosomally abnormal offspring.
How is PGD performed?
At West Coast Fertility centers highly skilled scientists and physicians work together to create embryos by In-Vitro fertilization.
After fertilization, one cell is removed from each embryo during its third day of development at the 8-cell stage. The PGD technique uses DNA probes that are a match for the chromosomes that are selected to be analyzed. Thus far we are able to screen for 8 pairs of chromosomes. Under a fluorescent microscope, the chromosomes and DNA probe together "glow in the dark" with a specific color for a given chromosome pair. Any extra chromosomes or a missing chromosome can be associated with birth defects or miscarriage.
For example, Trisomy 21, also known as Down syndrome, occurs when three chromosomes occur at the 21 position instead of the normal two chromosomes.
Utilizing the PGD technique, we can identify and transfer the normal embryos. At the same time, we are able to determine the gender of any embryo with 99% certainty. Gender identification is particularly important in cases of several sex-linked genetic diseases.
It should be noted that PGD is not 100% accurate. This is because scientists are able to analyze only one cell per embryo; however, we are able to detect about 90 to 95% of abnormal embryos.
PGD and Infertility Treatments
The rate of multiples (twins, triplets...) is much higher for those women undergoing fertility treatment. In order to increase the "odds" of an assisted reproductive technology, couples often request implanting a greater number of embryos to increase the chances that an embryo or embryos will implant. This can lead to higher multiple pregnancy rates which increase the risk for obstetrical complications, early labor and the delivery of premature babies.
By selecting PGD screened embryos we are able to increase the implantation rate and transfer a lower number of embryos which results in less pregnancy related complications.
PGD is an exciting technology that holds much promise for the future. At West Coast Fertility Centers, we feel a responsibility to our patients by providing the safest and most successful treatment possible. This includes helping to reduce the number of multi-fetal pregnancies with all their known risks. A major goal at our center is to improve the quality of life for patients and their offspring.
