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PGD and PGS in Atlanta, GA
Atlanta couples exploring family building options such as in vitro fertilization (IVF), surrogacy, or egg, sperm, or embryo donation, you can have embryos screened with preimplantation genetic diagnosis (PGD) or preimplantation genetic screening (PGS).
PGD and PGS screen embryos for chromosomal abnormalities (extra or missing chromosomes). 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.
Preimplantation Genetic Diagnosis (PGD)
Preimplantation genetic diagnosis (PGD) screens for single-gene defects that may cause genetic disorders and is often used by couples at risk of passing on inheritable genetic diseases to their embryos. The Atlanta fertility clinic knows what familial diseases the parents are at risk of passing on and uses PGD to diagnose an embryo as a carrier of a specific genetic mutation associated with diseases.
"PGD refers to taking a single cell from an embryo on Day 3 or six to eight cells from a Day 5 or 6 blastocyst for prevention of a genetic disorder such as Tay Sachs, Cystic Fibrosis or Sickle Cell Disease," says fertility doctor Mark Perloe, M.D., Medical Director of Georgia Reproductive Specialists in Atlanta. "Testing to rule out an unbalanced chromosomal translocation that might lead to miscarriage would also be considered PGD."
Genetic disorders PGD can help find include:
- Cystic fibrosis
- Down syndrome
- Huntington’s disease
- Muscular dystrophy
- Sickle cell anemia
- Marfan syndrome
- Tay-Sachs disease
In PGD for single gene mutation, the specialists will not discover any genetic mutations other than the ones they are specifically looking for. Common indications for PGD include:
- Previous birth of a child with a single gene disorder, such as Cystic Fibrosis, Tay Sachs, Muscular Dystrophy, Hemophilia, Thalassemia, fragile X or Sickle cell.
- Both partners are "carriers" for a single gene disorder based on screening tests and, therefore, at risk for passing on inherited genetic disease to their offspring.
Some fertility clinics allow patients to use PGD for gender selection; however there may be restrictions such as already having one child or being at risk for passing on an inheritable genetic disorder specific to one gender. "We do not offer gender selection unless specifically related to a medical condition," Dr. Perloe explains.
Preimplantation Genetic Screening (PGS)
Preimplantation genetic screening (PGS) is a screening test, which looks for structural abnormalities in chromosome number or size. The specialist searches for any structural chromosomal abnormality — usually in the number of chromosomes.
"Depending on the particular condition and methodology utilized, preimplantation genetic screening PGS can also be performed," Dr. Perloe says. "This involves screening all 24 chromosomes to determine embryos with the highest fertility potential by ruling out aneuploidy (extra or missing chromosomes)."
In the past, fluorescent in situ hybridization (FISH) has been used to look at structural abnormalities in the chromosome; however, only five to 10 chromosomes were examined. Studies have shown that this method has not been very beneficial.
A newer screening method, Microarray Comparative Genomic Hybridization (CGH), is a high-resolution test that can detect imbalances of chromosomes in much finer detail than achievable by conventional chromosome testing. Microarray CGH compares the levels of patient DNA to levels of a control (normal) DNA sample. The test delivers more complete genetic information about an embryo and is able to provide information about all 24 chromosomes. "Microarray CGH is the process done where a single cell is withdrawn on Day 3, or six to eight cells from the blastocyst biopsy are utilized to evaluate embryos for aneuploidy," Dr. Perloe says.
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. Atlanta fertility doctors may recommend PGS for couples who:
- Have had two or more miscarriages
- Have had two or more unsuccessful IVF attempts (two separate cycles)
- The female partner is over 35 and have had at least one miscarriage
- The female partner is age 39 or older
- There is severe male factor infertility, especially when a testicular biopsy is needed to obtain sperm.
Are PGD and PGS Safe?
PGS and PGD involve testing one cell of 3-day-old embryos or six to eight cells from a Day 5 or 6 blastocyst that has been created via IVF. 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.
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. "Safety and efficacy of embryo or blastocyst biopsy are largely dependent on the skill level of the embryologist," Dr. Perloe says. "Results vary widely from center to center. Studies have shown that blastocyst biopsies may be less traumatic as the later biopsy removes cells that have differentiated into the trophectoderm [future placenta] rather than taking cells that would make up the embryo."