Pre-implantation Genetic Diagnosis (PGD)

We are one of the most experienced clinics in the Pacific Northwest with regard to preimplantation genetic diagnosis (PGD). We have been carrying out embryo biopsies since 2003, allowing parents more choices than they were previously allowed in their reproductive health.

Our pregnancy rates are world class
Clinical Pregnancy Rate/Transfer: 42/71 = 59%              Implantation rate: 52/119 = 44%

Pregnancy rate/cycle start: 42/87 = 48%              Cycles with NO transfers: 16/87 = 18%

With our state of the art laboratory and fully trained staff we are a great choice of clinic if you require PGD testing for any reason at all. We constantly evaluate and then incorporate new technologies as appropriate.

Watch to Learn More About Pre-implantation Genetic Diagnosis (PGD)

Preimplantation Genetic Diagnosis (PGD) is a procedure used in conjunction with in vitro fertilization (IVF) to test early human embryos for serious inherited genetic conditions and chromosomal abnormalities before they are transferred to a woman’s uterus. PGD was first carried out in 1989 by Handyside and colleagues in London for a couple at risk of transmitting an X-linked disease. The procedure is sought by both fertile and infertile couples at high risk of having children with a serious genetic condition. It can also be used as a screening procedure to determine if an embryo is chromosomally normal prior to transfer. Before PGD the only testing option available to couples at risk of passing on a genetic disorder to their child was prenatal diagnosis. PGD offers another choice to carriers of serious genetic disorders and involves making decisions about the future of an affected embryo, rather than an affected pregnancy. PGD can be used to test for essentially any disorder that could be detected by amniocentesis – the list now numbers in the hundreds.

Each cell of the body contains structures called chromosomes within their centers or nuclei. A human cell typically contains 46 individual chromosomes, grouped as 23 pairs. The embryo will get 23 chromosomes from the sperm and the other 23 from the egg. These chromosomes are made up of genes, which are the blueprint that contains instructions as to how the cells within the body should function. It is very important, therefore that each cell contain a full complement of 23 pairs of chromosomes, as any imbalance in the number of chromosomal pairs (aneuploidy) can give rise to a failure of the embryo to implant, cause early pregnancy loss, or other conditions, such as Down’s syndrome. By analyzing the chromosomal content of early pre-implantation embryos it is possible to determine which embryos are more likely to implant and create a normal ongoing pregnancy.

PGD in action: a single cell is being removed from the embryo so it can be sent off and biopsied

In the case of testing for a genetic condition, a marker specific to the condition and the couple is developed prior to testing. This can then be used to specifically pinpoint any embryo that contains the gene disorder in question. In the case of a recessive condition, 2 copies of the gene disorder are required to exhibit the disease, and if only 1 is present then the embryo is considered to be a “carrier”. With dominant conditions, then the presence of just 1 copy will cause the disease to be exhibited. Therefore, a full genetic consultation is required prior to undergoing a single gene disorder PGD case.

PGD involves several steps:

  • the creation of an embryo via IVF (using ICSI for single gene disorders)
  • the removal of one or two cells from the embryo versus possible polar body or trophectoderm biopsy if appropriate
  • the genetic testing of these cells for specific genetic conditions
  • the subsequent transfer of unaffected embryos to a woman’s uterus

After removing a single cell from the embryo, the cell is either fixed onto a microscope slide or frozen in transport media before being shipped to a reference laboratory for analysis. This will then give us a picture of the chromosomal content of the embryo, and in conjunction with the embryo development score, the ability to predict more easily which embryos should be transferred during the cycle.

What is PGD used for?

Currently, PGD can be used for four different types of abnormalities:

  • single gene defects which cause disorders such as Cystic Fibrosis or Huntington’s disease
  • numerical chromosomal abnormalities (aneuploidy) which cause disorders such as Down syndrome (an extra chromosome 21) or Turner’s syndrome (females with one X-chromosome instead of two)
  • Structural chromosomal abnormalities such as various forms of translocations.
  • Gender selection / family balancing

Who may want to use PGD?

PGD can be used by both fertile and infertile couples. Couples who are carriers of a familial single gene disorder may wish to access PGD to have children without the particular genetic disorder. PGD for aneuploidy screening can also be used for couples who are having trouble conceiving, and it is also useful for couples who have suffered from repeated miscarriages. It may also be recommended for older patients in whom we know that the aneuploidy rate can be increased.

What are the potential benefits of PGD?

It allows for the selection of embryos with a normal chromosomal content.

PGD offers people at high risk of transmitting a serious genetic condition to their children an alternative to their existing options of:

  • avoiding conception
  • attempted natural conception, involving a known risk to the health of the future child
  • attempted natural conception, and pregnancy termination if the fetus is found to be affected by the condition following prenatal diagnosis
  • using donated gametes or embryos in an attempt to conceive an unaffected child.

For many people, termination following prenatal diagnosis is either unacceptable or less preferable because of:

  • ethical concerns based on beliefs about the moral status of the fetus
  • emotional trauma associated with a termination following a much desired pregnancy
  • health risks associated with possible repeated terminations.

What are the concerns associated with the use of PGD?

PGD can only be used in conjunction with IVF. The live birth rate for PGD is similar to the live birth rate for conventional IVF. Despite the relatively wide acceptance of PGD in the clinical arena, it remains a technically demanding procedure. It is subject to a risk of contamination and misdiagnosis, particularly when it is used for single-gene disorders. PGD involves the use of highly technical molecular biology techniques, and the error rates can be anywhere from 5-22%. While PGD is diagnostically reliable, we still advise our patients to undergo prenatal diagnosis to ensure that the pre-implantation diagnosis is accurate, and to test for any abnormalities not screened for during PGD.

Although many clinics in the US offer aneuploidy screening to couples having trouble conceiving or carrying a baby, no consistent evidence is available to show that aneuploidy screening improves the live birth rate for couples having fertility problems.

What are the ethical issues associated with PGD?

Discarding affected embryos

PGD involves making a decision about the fate of affected embryos prior to pregnancy, at a very early stage of development. This is in contrast to prenatal diagnosis, which requires a decision to be made about terminating an existing pregnancy, at a much later stage. For many people, discarding embryos is likely to be ethically less problematic than terminating a fetus. For others, both abortion and PGD may be unacceptable.

PGD for Human Leukocyte Antigen tissue typing

Human Leukocyte Antigen (HLA) tissue typing or tissue matching is an additional step to PGD to determine if an embryo could lead to the birth of a child who is a tissue match for an ill sibling.

For some people, HLA tissue typing raises many ethical and social questions. One of the most significant issues is whether people should be able to select an embryo on the basis that the child born may be the source of life saving therapies for a sibling.

Can PGD be used to select the sex of a baby?

Yes. The use of PGD for sex selection is carried out for two major reasons. The first is to prevent transmission of sex-linked genetic conditions, when a specific test for the condition is not available. This medically-based rationale is acceptable to most. The second reason, a social one, is to provide parents with a child of the preferred sex. We allow couples to specify sex and pursue “family balancing” after they have had at least one child of the opposite sex and have fully discussed with us the pros and cons as well as the risks and benefits of such an approach.

Can PGD be used to “design” babies?

In principle, PGD can be used to select for or against any characteristic that has a genetic origin. Some contend that PGD could be used to select against obesity, or hyperactivity, or for intelligence, beauty, or athletic ability. However, the use of PGD for these purposes is not currently scientifically possible.

For some, any selection of embryos is regarded as leading to designer babies. However, PGD does not allow people to determine the precise characteristics of embryos.

PGD Implantation and Pregnancy Rates

Clinical Pregnancy Rate/Transfer: 42/71 = 59%              Implantation rate: 52/119 = 44%

Pregnancy rate/cycle start: 42/87 = 48%              Cycles with NO transfers: 16/87 = 18%

 

Year # cycles initiated # with no transfer # pregnant # embryos transferred # embryos implanted
2003 3 2 0 2 0
2004 15 1 7 24 10
2005 11 1 6 16 7
2006 8 4 3 6 4
2007 11 3 5 15 7
2008 10 0 9 18 10
2009 7 1 3 8 4
2010 10 1 6 16 8
2011 12 3 3 14 2
Totals 87 16 42 119 52

For live birth rate information please visit the CDC website.

Please contact us if you have any questions.We are proud of our PGD program and our IVF success rates are world class. As a patient of ORH you can feel secure that you will receive the best care possible.