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PREIMPLANTATION GENETIC DIAGNOSIS

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What is preimplantation genetic diagnosis?

Preimplantation genetic diagnosis (PGD) is technology used to identify a genetic mutation in an embryo created through in vitro fertilization (IVF) before implanting the embryo into the uterus.  The purpose of PGD is to identify an unaffected embryo for implantation, thereby reducing or virtually eliminating the risk of having a child with certain genetic diseases.

The first baby born using this technique was born in 1989.  As of 2001, more than 700 babies had been born following PGD. 

How is a diagnosis made with PGD?

There are different techniques used for certain indications and varying by center.  In general, PGD involves extracting genetic material from the embryo for analysis.  Removing a cell from the embryo for genetic analysis does not hurt the embryo.  The embryo compensates for the removed cell and continues to divide normally.  This genetic material is then used to test and see if the embryo has a mutation.

Who might consider PGD?

Families with a high risk of having children with a genetic disorder or chromosome abnormalities and who wish to avoid elective pregnancy termination or to prevent the birth of an affected child following prenatal diagnosis may consider PGD.  Performing genetic diagnosis prior to implantation of the embryo may reduce the potential for termination of affected fetuses diagnosed by prenatal testing. 

What is the pregnancy rate?

There is no difference in pregnancy rates for couples going through IVF and PGD and couples doing IVF alone.  The rates are age dependent, but as a general rule it is 30-40% per IVF cycle.

Does PGD eliminate the need for amniocentesis and other prenatal testing?

At this time, prenatal diagnosis by chorionic villus sampling (CVS) or amniocentesis is still recommended for reassurance and confirmation of PGD since this technology is not guaranteed.  However, prenatal testing is a personal decision that every couple must make for themselves.

What other genetic disorders would benefit from PGD?

PGD has been attempted for various single gene disorders including cystic fibrosis, Tay-Sachs disease, alpha-1-antitrypsin deficiency, retinitis pigmentosa, hemophilia A, Alport disease, sickle cell disease, thalassemia, X-linked hydrocephalus, and myotonic dystrophy among others.  It is possible to do PGD for most genetic disorders with an identifiable mutation. 

What is the cost?  Does insurance cover this?

The cost for PGD is usually more than $20,000.  In rare instances, insurance companies have been found to cover the PGD procedures.  Some insurance companies will cover the IVF procedures (although usually this requires a diagnosis of infertility).  Since PGD is still considered investigational by insurance standards, it is unlikely that they will consider covering this type of procedure.

Is PGD controversial?  

There are some people who have voiced opinions against the use of PGD.  Some of these reasons include worrying that PGD will be used to design the “perfect baby” as well as the fact that fertilized cells that have a mutation are not implanted and are allowed to die in the dish. 

Where do I go for more information?

There are more than 50 centers worldwide that offer PGD.  A good place to start if you are interested in PGD is to contact a local physician or fertility specialist.  Many physicians and fertility specialists have working relationships with certain PGD centers that they can refer you to.  Also, some parts of the process of PGD may be performed at a local IVF center.  Additionally, many PGD centers have websites where you can access more information.

References

Reproductive Genetics Institute
www.reproductivegenetics.com

JJ Marick, MD. emedicine: Preimplantation genetic diagnosis. 
www.emedicine.com/med/topic3520.htm

Written By Andrea Harbison, MS and Hope Northrup, MD

**Tuberous Sclerosis Alliance Information Sheets are intended to provide basic information about TSC. They are not intended to, nor do they, constitute medical or other advice. Readers are warned not to take any action with regard to medical treatment without first consulting a physician. The TS Alliance does not promote or recommend any treatment, therapy, institution or health care plan.

Made possible through an educational grant from the Schnurmacher Foundations.  June 2006