PGD Testing and Diagnosis - Phoenix, Scottsdale, Arizona The Phoenix Preimplantation Genetic Diagnosis Center Director, Mark D. Johnson, M.D., FACOG, FACMG Arizona Reproductive Medicine Specialists (ARMS)

The Phoenix Preimplantation Genetic Diagnosis Center collaborates with two internationally recognized molecular genetics pioneers and experts in the field of Preimplantation Genetic Diagnostics: Mark R. Hughes, M.D. Ph.D. of Genesis Genetics Institute and Santiago Munne, PhD. of Reprogenetics. We collaborate with these internationally recognized laboratory PGD experts to provide our patients with the highest quality assurance for precise and accurate genetics diagnostics in their embryos. The Phoenix Preimplantation Genetic Diagnosis Center is the most experienced leader in providing excellence and the highest quality assurance in embryonic genetic disease diagnostics in the Southwest.

Preimplantation Genetic Diagnosis – What is it?

Preimplantation Genetic Diagnosis (PGD) is the screening and detection of genetic diseases or chromosome abnormalities in eggs or embryos prior to establishment of an intrauterine pregnancy in order to produce healthy children. The advantage of PGD is that couples at increased risk for producing children with incurable genetic diseases or chromosomal disorders are provided the opportunity to reproduce without the increased risk of having a child with an incurable disease or chromosomal abnormalities.

The PGD process is accomplished by removing one or two cells from the early embryos as they develop in culture in the in vitro fertilization (IVF) laboratory. These cells undergo genetic analysis to determine which embryos are chromosomally normal or not affected with the specific genetic disease under study. Results of the PGD testing are available within two days and only those embryos determined to be chromosomally normal or not affected with genetic disease are transferred into the uterus to establish a pregnancy.

PGD for genetic disease is able to be performed for a majority of single gene disorders in which the disease gene mutation has been isolated and is detectable through a process of DNA analysis know as polymerase chain reaction (PCR). PGD screening for chromosome quantification through fluorescent in situ hybridization (FISH) is able to be performed for the majority of chromosome abnormalities involved in fetal abnormalities and miscarriages.

While there are limits to PGD at the present time, the development of this technology has enabled more than one thousand children to be born worldwide that are free of incurable genetic diseases or chromosome abnormalities.

Preimplantation Genetic Diagnosis – Who is it for?

PGD, or genetic testing performed on eggs or embryos, is a valuable adjunct to the process of IVF. Although it may become a routine part of the IVF process in the future, currently PGD is available as a reproductive option for couples in three general categories.

1. PGD may be an option for a couple when an individual partner is a carrier or both partners are determined to be carriers for an inheritable genetic disease and the risk of producing a child with an incurable genetic disease is 25% to 50%. Common genetic diseases that have been screened by PGD are cystic fibrosis, sickle cell anemia, Tay Sachs Disease, Huntington Disease, myotonic dystrophy, and numerous other diseases that are caused by genetic mutations.

2. PGD may be an option for couples who are at increased risk for producing abnormal embryos with an abnormal number of chromosomes (aneuploidy), such as couples with unexplained recurrent miscarriages and woman of increased reproductive age. As women progress through normal aging, they produce a larger number of abnormal eggs with aneuploidy, which gives rise to reduced fertility and an increased rate of miscarriages and fetal aneuploidic conditions, such as Down Syndrome. The rate of aneuploidy in eggs from women older than forty years is greater than 50%. Genetic testing to differentiate the embryos with a normal number of chromosomes from the embryos with an abnormal number of chromosomes in embryos reduces the possibility of having an abnormal pregnancy. PGD screening for aneuploidy with FISH technology does not increase the couple’s chances of becoming pregnant, but rather it increases the chance for producing a normal pregnancy and reduces the risk of early pregnancy loss, recurrent miscarriages, and fetal aneuploidic conditions such as Down Syndrome.

3. Couples in which one of the partners is a carrier for a chromosome rearrangement, such as a balanced translocation or inversion, are at increased risk to produce chromosome abnormalities in their embryos resulting in increased rates of miscarriages and fetal abnormalities. PGD has been shown to increase the chance for producing a normal pregnancy and improve outcomes in pregnancies conceived from carriers of balanced chromosome rearrangements.

Why consider Preimplantation Genetic Diagnosis?

Prior to the availability of PGD, couples at increased risk for producing children with incurable genetic diseases or chromosomal disorders conceived pregnancies and were provided the option of undergoing prenatal diagnosis to determine if their fetus is affected with a specific genetic disease or chromosomal disorder. The problem with prenatal diagnosis is that it is performed after a pregnancy is established and if it is determined that a fetus is affected with a specific genetic disease or chromosomal disorder, the couple must confront the difficult decision of having an affected child or pregnancy termination. The methods of prenatal diagnosis are chorionic villus sampling performed between ten to twelve weeks of the first trimester and an amniocentesis performed after the fifteenth week of the second trimester. Although first trimester biochemical and ultrasound testing are available to assist in determining pregnancies at high risk for chromosome abnormalities, they are still considered screening tests and are not yet confirmatory diagnostic tests.

Besides PGD and prenatal diagnosis, other reproductive options available for couples with increased genetic reproductive risks are the use of donor eggs or donor sperm and adoption. PGD is safer than elective second trimester termination, psychologically more acceptable than elective termination, and it provides couples at increased risk for producing children with incurable genetic diseases or chromosomal disorders with more reproductive options than donor eggs or donor sperm, adoption, and sterilization.

Prospective couples considering PGD should initially consult with a Board Certified Clinical Geneticist, such as Dr. Johnson, or a certified Genetic Counselor to review their family histories and help couples to understand their genetic reproductive risks. After your genetic counseling and diagnostic evaluation, Dr. Johnson and the physicians and staff of the Phoenix PGD Center at ARMS will assist you in having a healthy baby.

Couples interested in learning more about PGD should contact Dr. Johnson at Arizona Reproductive Medicine Specialists (ARMS) at 602-343-2767 or at his e-mail at mjohnson@arizonarms.com.

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