What Is Preimplantation Genetic Diagnosis (PGD)?
Pre-implantation genetic diagnosis (PGD) is a genetic testing procedure performed on embryos created with in-vitro fertilization by examining an embryo for a specific genetic mutation known to cause serious disease. It enables people with an inheritable condition in their family to avoid passing it on to their children.
Preimplantation Genetic Diagnosis (PGD) Cost in Iran
The cost of Preimplantation Genetic Diagnosis (PGD) in Iran starts from $1200.
Who Should Consider PGD?
PGD prevents pregnancy termination because it allows the selection of an embryo free of the genetic disease at issue before pregnancy is established. PGD is available for almost any inherited condition for which the exact mutation is known. PGD is suitable for:
. Individuals with a chromosomal re-arrangement, for example, chromosomal translocation in which a segment of a chromosome is found at a location other than its normal place.
. Individuals with known single gene disorders, e.g. cystic fibrosis, cystic disease, Tay Sachs disease.
. Couples who wish to match stem cells when a family member needs a tissue donor.
. Couple with a child known to have a genetic mutation.
Preimplantation Genetic Diagnosis Process Step-by-step
. Step1: Stimulation of the ovaries
To create embryos for genetic testing, the ovaries have to be artificially stimulated using hormones to produce several eggs at the same time.
Because a significant number of a couple’s embryos are likely to be affected by genetic or chromosomal abnormality, a large number of embryos need to be created for the best chances of success.
. Step 2: Collection of eggs from the ovaries
At the appropriate time, the eggs are removed during a surgical procedure known as egg retrieval. Once the eggs are removed, they are examined to determine which of the eggs are mature and normal.
. Step 3: Insemination/injection of sperm
Fertilization during PGD will be done either by:
. In Vitro Fertilization (IVF): Sperm and eggs are placed together in a culture dish to allow fertilization to occur.
. Intracytoplasmic Sperm Injection (ICSI): A single sperm is injected into the center of an egg. This technique is used for conditions caused by a single faulty gene.
. Step 4: Fertilization
The morning after injection/insemination of the sperm, the embryologist carefully examines each egg to see if fertilization has occurred.
. Step 5: Embryo biopsy
The eggs that were successfully fertilized are grown in the laboratory for 5-6 days, during which time the embryo forms a blastocyst of about 100-150 cells. At this stage, trophectoderm biopsy (the cells that will form the placenta) takes place.
The removal of these cells should not harm the embryo.
. Step 6: Embryo Testing
The cells are tested to see if the embryo they were removed from has abnormalities that cause genetic conditions.
. Step 7: Embryo Transfer
Only embryos that do not have certain genetic conditions that have been tested for are transferred to the woman’s uterus. Usually, one embryo is transferred to the uterus at a time to prevent the possibility of multiple births (more than one baby in a pregnancy).
Any remaining healthy embryos suitable for later use will be frozen.
Those embryos that are affected by the inherited condition are allowed to perish or couples are asked if they would consider allowing these embryos to be donated for research and training.
. Step 8: Pregnancy Test
The woman is given a pregnancy test 12 days after embryo transfer. A positive pregnancy test means that an embryo has been implanted.
What Risks Are Involved?
The IVF and PGD process carries risks for the woman and the embryo. These may include:
. An embryo may not develop after fertilization of an egg.
. Health risks of the IVF cycle.
. The embryo may not develop after biopsy.
. Not all embryos will be suitable for biopsy.
. Test results may be inconclusive.
. There may not be any unaffected embryos available for transfer.
. No pregnancy is achieved, even after the transfer of an unaffected embryo.
. Results are not 100% accurate.
What Are the Advantages and Disadvantages of PGD?
Genetic counseling is important when considering all the options for planning a pregnancy. The pros and cons of each option are complex and vary depending on a couple’s situation.
The option of IVF and PGD allows couples to reduce the chance of having a child with a specific genetic condition without having to face the difficult decision of whether to stop a naturally conceived pregnancy that is affected by testing during pregnancy.
IVF/PGD can also reduce the risk of recurrent miscarriages for couples where, for example, one partner carries a chromosome translocation.
As with any IVF procedure, stress and sometimes frustration arise when undergoing the PGD process. Success rates for having a child from an IVF cycle followed by PGD vary from IVF center to center (these are available from the individual IVF provider) but tend to follow standard IVF success rates.
Couples may balance the financial and emotional costs of IVF followed by PGD with the consideration of terminating the pregnancy or continuing the pregnancy for a child with a genetic condition conceived naturally.
What Is the Chance of Having a Baby with PGD?
It is difficult to assess the success rate for PGD because little data is currently available. As with most fertility treatments, success depends on many factors, including the woman’s age and weight.
Additionally, sometimes no embryo is suitable for transfer to the uterus, for reasons including:
. Embryos do not develop to the blastocyst stage.
. Not enough eggs were produced or fertilized.
. Embryos do not survive the biopsy, although this is a rare event.
. All the embryos were affected by the genetic condition.
Therefore, a pregnancy cannot be guaranteed using PGD.
Accuracy of Preimplantation Genetic Diagnosis
The accuracy of PGD will vary and it is possible that the test is not 100% reliable or conclusive. However, testing is 98-99% accurate for most couples. The risks depend on the condition for which PGD is being offered and the couple’s test results.
If PGD results in pregnancy, all patients are offered confirmatory prenatal testing (amniocentesis or chorionic villus sampling).
FAQ:
- Does Preimplantation Genetic Diagnosis Harm the Embryo?
Clinical studies show that embryo biopsy with PGD does not affect the ability of the embryo to attach, but it does affect embryo viability.
- Does Preimplantation Genetic Diagnosis Cause Congenital Problems?
Any congenital problems in children born with PGD are no different from those in pregnant women who conceive naturally.
- What Are Chromosomal and Genetic Conditions?
Chromosomal conditions are caused by having either extra or missing genetic material or a rearrangement in chromosome structure. Some chromosome problems are severe and may result in miscarriage or failure to conceive. If a baby is born with a chromosomal problem, they may have developmental problems and/or mental retardation. Women over 35 are at higher risk of having a pregnancy affected by chromosomal conditions. A person can have a genetic condition if one of his or her genes does not function properly. There are many different types of genetic conditions. Couples who are known or suspected to be at risk for having a pregnancy affected by a genetic condition are candidates for PGD.
