Preimplantation Genetic Diagnosis, also referred to as PGD testing, is an advanced technology used along with IVF to check your embryos for genetic defects, before implanting them in your uterus.
Using this “embryo biopsy” technique, the embryologist can test the embryos for abnormalities in chromosomes as well as hereditary conditions. PGD is helpful for patients who are carriers of chromosomal or genetic disorders and fear passing them on to their children.
Although initially there were some concerns regarding the use of this technology, but it has been proven safe over trials and uses of many years and is widely used with IVF cycles today.
What is the difference between PGD and PGS?
Unlike PGD, Preimplantation genetic screening (PGS) does not check the DNA or identify a specific genetic disease. It is simply used to check the embryos for aneuploidy (abnormal numbers of chromosomes), which is the main cause of miscarriage and implantation failure, causing frustration to a lot of IVF patients.
Disorders like Down’s syndrome—caused by the presence of an extra chromosome 21—can be avoided with PGS.
Using PGS the doctor can simply identify the embryos that have too many or too few chromosomes, so those can be left behind and only the normal ones are transferred, thus raising the possibility of successful pregnancy.
Read more about the uses and benefits of PGS.
PGD on the other hand is significantly more complex as it examines the genes that make up the chromosomes and checks them for specific diseases. So, if there is any indication of you or your partner having any history of genetic diseases, you will likely need PGD.
How is PGD performed?
First, the normal process of in vitro fertilization will be carried out in which the egg and sperm are fertilized in the lab. The resultant embryo will divide into multiple cells in the next three to five days.
PGD-IVF process will be performed over that embryo in the following steps:
Biopsy: Either one cell is removed at day three and several cells are removed at day five (blastocyst stage) of the embryo. The day-5 biopsy on blastocyst is considered by many experts to be the gold standard for PGD testing.
DNA evaluation: While the embryo is frozen in the lab, the DNA of extracted cells is evaluated to check for presence of any problematic gene.
Embryo Selection: The embryos that pass as problem-free will be transferred to the uterus and if there are still other good ones left, they will be kept frozen for future use.
How much time is required for PGD?
If you opt for PGD testing with IVF, you will have to wait 10-14 days extra to allow for the screening of embryos before implantation.
In some clinics, you can also have PGD done on fresh embryos (day 3) and have the embryos implanted on day 5. However, PGD testing on day 3 embryos can be harmful for them and it may also not show accurate results because the cells have not completely developed by that stage.
PGD testing on day 5 of embryo development (blastocyst stage) and transfer of frozen embryos is recommended for best results. If you are going abroad for IVF-PGD, it is best to plan two trips (one for egg pickup and the other for embryo transfer), or one long trip of 6-7 weeks.
Do you need PGD with IVF?
PGD is advised if you can identify with any of the following situations:
- You have family history of sex-linked genetic diseases
- You are a carrier of single gene disorder
- You have a previous child with a genetic problem
- You or your partner is a carrier of chromosomal translocations
- You have had recurrent miscarriages
- You have suffered repeated IVF failure
With PGD your doctor can identify translocations in chromosomes (rearrangements of parts of chromosomes) as well as single mutations in genes that can cause genetic diseases.
PGD can effectively identify embryos for genetic disorders such as Tay-Sachs disease, cystic fibrosis, sickle cell anemia, muscular dystrophy, fragile X, thalassemia, and about 4,000-single gene disorders.
It is also helpful to raise your chances of success if are seeking IVF in advanced age —after 36 years, as there is a greater chance of chromosomal anomalies in female eggs as they get older.
Look at the below chart from the New England Journal of Medicine
If there is no reason to suspect genetic problems and you are only getting genetic testing to improve your chances of success in IVF, you may be recommended to undergo PGS instead of PGD.
Cost of PGD
The cost of PGD testing is determined by the number of embryos and for upto 5 embryos the average costs are as below:
IVF with PGD in Thailand – starts from $12,500
IVF with PGD in Malaysia – starts from $12,000
IVF with PGD in India – starts from $5,000
Advantages of PGD
- With the help of PGD testing, over a hundred different genetic diseases can be detected
- It allows you to see of potential problems in the embryo to let you decide if you want to continue with the pregnancy
- By detecting aneuploidy, PGD shows the probability of miscarriage and implantation failure and thus allows for greater IVF success
- It also allowed for sex detection to help couples balance their families but since people started abusing it and the government declared sex detection illegal, doctors in many countries stopped offering it.
Please note: PGD-PGS testing is not offered for gender selection. It is strictly offered to analyze the genetic content of embryos to improve the chances of IVF success.
Criticism and Risks of PGD Testing
- Extra time needed before embryo implantation
- If the results are not recorded carefully, an embryo with a chromosomal defect could be transferred to the uterus and healthy embryos are discarded
- Not all genetic diseases can be detected – like the ones that begin to show only when the carrier reaches middle age. PGD greatly improves the chances of conceiving a child without a genetic disorder but it does not completely eliminate the risk.
Is PGD testing safe?
Some people believe that taking cells for a biopsy so early on could disturb the embryo but data from years of PGD tests reveals that these tests do not raise the risk of birth defects in a new born.
Embryos are delicate and PGD is quite a sophisticated procedure, so there is some measure of risk if the process not handled carefully. Infertility Aide only works with the doctors that have extensive experience and have been using these technologies successfully for years.
It is rather unsafe to carry on IVF without PGD (in cases where it is especially indicated) and risk a miscarriage or carry a baby with a serious genetic disorder to birth.
Alternatives to PGD testing
Preimplantation genetic testing is done on embryos in the IVF procedure but AFTER the pregnancy is confirmed, there are some tests that can be done for genetic abnormalities:
- Chorionic villus sampling (CVS) – biopsy of the placenta at 10 -12 weeks of pregnancy to detect for fetal genetic abnormalities. If detected, you may have to consider an abortion.
- Amniocentesis – performed 16 to 18 of pregnancy. In this test the amniotic fluid is checked for genetic abnormality in the fetus.
- Ultrasound & blood tests – additionally help in checking for some abnormalities. If suspected, advanced tests may be recommended to confirm the diagnosis.
IVF with donor eggs or donor sperm may be considered if there is a high risk of transferring genetic problems to the baby.
For more information on IVF with PGD and to know about the price of IVF with PGD testing, get in touch via the form on the right.
References:
http://americanpregnancy.org/infertility/preimplantation-genetic-diagnosis/
http://www.hfea.gov.uk/preimplantation-genetic-diagnosis.html