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Preimplantation Genetic Diagnosis
If you’re exploring high-tech family building options such as in vitro fertilization (IVF), surrogacy, or egg, sperm, or embryo donation, you can have your embryos screened with preimplantation genetic screening (PGS). PGS does not in fact diagnose diseases but screens embryos for chromosomal abnormalities (extra or missing chromosomes).
Many women who use IVF are older in maternal age (35 plus), which places them at increased risk for conceiving a child with Down syndrome or other chromosomal disorders. Doctors may recommend PGS for women who:
- Have had two or more miscarriages
- Have had two or more unsuccessful IVF attempts (two separate cycles)
- Are over 35 and have had at least one miscarriage
- Have had multiple miscarriages or failed IVF attempts
Preimplantation genetic diagnosis (PGD) screens for single-gene defects that may cause genetic disorders including:
- Cystic fibrosis
- Down syndrome
- Huntington’s disease
- Muscular dystrophy
- Sickle cell anemia
- Marfan syndrome
- Tay-Sachs disease
Developed during the early 1990s, PGD is also used by couples at risk of passing on inheritable genetic diseases to their embryos.
Historically, physicians used the term “PGD” when referring to screening or diagnosis, but that trend is shifting, and many now differentiate between PGS and PGD.
What It Is
PGS/PGD involves testing one cell of 3-day-old embryos that are created via IVF. These young embryos have just four to eight cells. One cell is removed and carefully examined for genetic abnormalities. At this early stage of development, all embryonic cells have the same genetic makeup and potential for development; they simply continue to divide without the removed cell.
In PGS/PGD, geneticists and specialists examine and analyze the embryos and if a problem is found the woman or couple can decide to transfer only the “good” embryos. The risk of damaging embryos at this stage is small and studies have shown that PGS/PGD does not increase the risk of birth defects. It’s important to recognize, however, that screening and diagnosis are not 100 percent accurate. As a result, PGD is not considered an alternative to the two primary screening tests used during early pregnancy — amniocentesis and chorionic villus sampling. Most genetic counselors would recommend an amniocentesis and chorionic villus sampling post PGD cycle.
PGS/PGD costs from $2,500 to $7,000 and is not covered by most medical insurance policies.