PGD: Pre-implantation Genetic Diagnosis

PGD is an optional procedure that may be performed during an in-vitro fertilization (IVF) cycle, and makes use of genetic testing to screen embryos for genetic or chromosomal abnormalities. Only embryos found to be free of the tested condition are selected to be transferred into the woman’s uterus.

PGD can increase the chance that pregnancy occurs, dramatically reduce the risk of early miscarriage, and lower the odds of birth defects.

Who can benefit from PGD?

Women with advanced maternal age. As a woman ages, she becomes more likely to have more abnormal eggs, and fewer normal eggs. PGD can screen out chromosomally abnormal embryos, so that only embryos with the best chances of resulting in pregnancy are selected.

Couples with recurrent pregnancy loss. The majority of first trimester miscarriages are due to chromosomal abnormalities. Using PGD to select only normal embryos can drastically reduce the risk of early miscarriage.

Couples with several failed IVF cycles. Without PGD, embryos are selected based on appearance only. While an embryo’s appearance (or morphology) can give clues about its growth and development, it can also be misleading. The most perfect-looking embryo may have hidden chromosomal defects preventing any possibility of pregnancy; while a less-than-beautiful embryo might in fact have the best chance of becoming a healthy baby. PGD improves the odds for a successful IVF cycle by accurately identifying the best embryos for transfer.

Men with severe male factor infertility. If a man has few normal sperm, and a high proportion of abnormal sperm, more abnormal embryos are likely.

Couples at risk of passing on a sex-linked genetic disorder. PGD can determine the embryo’s gender, allowing couples to select only females if they are carriers of a disease affecting only males.

Couples at risk of having a child with a specific inherited genetic disorder. PGD can assure parents who are carriers of a single gene disorder, such as cystic fibrosis, Tay-Sachs disease, sickle cell anemia, or many others, that their baby will not inherit the disease by screening out affected embryos.

How is the PGD procedure performed?

After being incubated for about 3 days, one or two cells are carefully removed from the embryo for genetic testing. See PGD Procedure for more details.

What are the types of PGD testing?

PGD for chromosome abnormalities (aneuploidy). The most common type of PGD identifies embryos with the incorrect number of chromosomes. This condition, called aneuploidy, is nearly always incompatible life, and is the cause of most early miscarriages.

PGD for single-gene disorders. PGD can diagnose embryos with a specific genetic disease, allowing parents to avoid passing on a heritable genetic disorder.

What are the disadvantages of PGD?
  • Additional cost.
  • Infrequently, an embryo does not survive after the embryo biopsy. See PGD Procedure for more information.
Does PGD guarantee that a baby will have no birth defects or diseases?

No. Although PGD can eliminate many of the most common chromosomal and genetic defects, no test exists that can guarantee perfect health.

  • PGD testing is limited because only one or two cells are available for testing; and analysis must be performed very rapidly, in time for an embryo transfer within the next 48 hours.
  • The genetic basis for many diseases and defects is not known, or is impractical to test for.
  • Although many genetic diseases can be tested with PGD, not all tests can be performed on the same embryo.
Can PGD correct chromosomal and genetic flaws?

No, PGD can only detect and screen out abnormal embryos. Although the media has coined the term “designer baby”, PGD is simply a testing technique, not a design process. Further, traits such as eye color, intelligence, or athletic ability cannot be determined by PGD.