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What is PGD?
Developed in the early 1990's, preimplantation
genetic diagnosis (PGD) is a way for couples to prevent a pregnancy affected
by a genetic condition or chromosomal disorder. There are various types of
PGD available, depending on the needs of the individual couple. This form of
genetic testing is performed on eggs or embryos during an in vitro fertilization
(IVF) cycle. The eggs or embryos that have been analyzed and are found to be
normal are transferred into the woman's uterus, where, hopefully, they
will implant and result in the birth of a healthy child.
Currently, we are able to perform PGD for many genetic conditions including
single gene disorders and chromosomal abnormalities. At the Reproductive Genetics
Institute, we have been performing PGD since it became available in 1990. We
pioneered the polar body removal technology and are one of the most active
centers offering PGD in the world. Our laboratory staff has extensive experience
in the techniques involved with PGD.
How can PGD help me?
PGD can significantly reduce the chances for your baby to be affected with
a specific genetic condition or chromosomal abnormality. We are able to test
for many different diseases, including aneuploidy conditions, single gene disorders
and chromosome translocations.
Many couples request PGD for aneuploidy conditions,
such as Down syndrome, trisomy 18, trisomy 13 and Turner syndrome. Aneuploidy
conditions typically do not run in families. However, up to 60% of early
miscarriages are due to aneuploidy conditions, and the risk for aneuploidy
increases with a woman's age. The purpose of PGD for aneuploidy is to increase a couple's
chance for pregnancy, reduce their risk for miscarriage, and improve their
overall chance of bringing home a healthy baby after in vitro fertilization.
Other couples request PGD for a specific genetic condition running in their
family, such as Tay Sachs disease, cystic fibrosis, muscular dystrophy, Fragile
X syndrome or spinal muscular atrophy. Our center has extensive experience
testing for many single gene disorders, including rare genetic
syndromes.
For individuals who carry a chromosomal translocation, PGD
can be used to test eggs or embryos for their specific translocation. This
greatly decreases the risk for miscarriage and/or the birth of a child with
birth defects and mental retardation associated with an unbalanced chromosome
translocation.
We can also test for the HLA status of embryos. This is
requested by couples interested in having a child who is a healthy bone marrow
match to another family member. HLA testing can be performed while testing
for a specific genetic condition, such as beta-thalassemia.
What conditions are tested?
The conditions tested include:
How is PGD performed?
Our geneticists use a variety of techniques for PGD including:
At present, RGI is the only center in the world offering Preimplantation Diagnosis
by sampling the first and second polar bodies. The first polar body is discarded
during oocyte maturation, prior
to fertilization and contains one set of duplicated chromosomes (with two chromatids
in each chromosome), while the second polar body is discarded after fertilization
and contains one set of chromatids. By
testing the first and second polar bodies for a specific genetic disease, the
geneticists can determine whether the woman's eggs carry the corresponding
gene. The procedure is offered to couples who are known
carriers of genetic diseases detectable by DNA analysis. RGI physicians have
already performed over 100 clinical cycles involving preimplantation diagnosis
for cystic fibrosis , thalassemia, Tay-Sachs disease,
sickle cell disease, and other diseases (click here for list), resulting in
many ongoing pregnancies confirmed to be unaffected by CVS or amniocentesis
as well
as
the birth of two dozen healty children.
The other important application of the polar body testing is preimplantation
diagnosis of Down syndrome
and other common aneuploidies. Many patients referred to In Vitro Fertilization
program (IVF) are of advanced maternal age (35 years of age or older at the
time of delivery), which places them at elevated
risk for conceiving a child with an extra chromosome and thus delivering a child
with Down syndrome (extra chromosome 21) or other common trisomies (Trisomy
13 and 18). Aneuploidies may also result in
spontaneous abortions (miscarriage) or nonimplantation, decreasing considerably
the chances of the patient achieving a pregnancy. Therefore, by testing for
the conditions beforehand, we can prevent
these events. Polar body removal involves the removal of the first and second
polar bodies and analysis of the chromosome number in both the first and second
polar body by FISH. Only embryos resulting from
the fertilization of eggs with normal number of the chromosomes (chromosomes
13, 16, 18 ,21 and 22)
are transferred. The patients may choose which embryos they wish to be transferred
or frozen. The procedure has been offered to over 600 IVF couples and resulted
in 131 births of healthy children
and dozens ongoing pregnancies confirmed to be unaffected by CVS or amniocentesis.
This has also improved the pregnancy rate, compared to patients of advanced
maternal age without polar body
diagnosis.
Preimplantation diagnosis based on blastomere biopsy is also performed at our
Center. The most common application of blastomere biopsy in RGI is preimplantation
sexing by FISH to avoid the pregnancy with
X-linked disorders, such as hemophilia A and muscular dystrophy, or for single
gene disorders in
which the male partner is affected.
How much does PGD Cost?
Please review our price list. If you have any questions, please feel free to
contact
us for
further details.
How do we get started?
Please review our PGD information packet and pamphlet and contact our genetic
counselors at 773-472-4900 or e-mail us with
any questions or inquiries regarding our PGD program.
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