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What is the Preimplantation Genetic Diagnosis (PGD)?

What is the Preimplantation Genetic Diagnosis (PGD)?

What is the Preimplantation Genetic Diagnosis (PGD)?

Preimplantation Genetic Diagnosis (PGD) is an assisted reproductive technology (ART) used for the genetic testing of embryos. By using PGD to study an embryo’s genes, your fertility doctor can find out which embryo has the best chance of growing into a healthy baby. The main aim of the PGD test is to increase the chances of healthy embryo implantation to achieve a successful pregnancy.

When talking about the key difference between PGS (Preimplantation Genetic Screening) and PGD (Preimplantation Genetic Diagnosis) is that a PGD detects specific genetic conditions whereas PGS is like a health screening performed on an embryo to assess the general well-being of an embryo, without going into specific genetic conditions of that embryo. PGD is used along with an IVF cycle to increase the potential for a successful pregnancy and delivery.

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What you should know about PGD?

Preimplantation Genetic Diagnosis is performed when the doctor is looking out for a specific genetic disorder and it is a procedure done before implanting the embryos to help detect genetic defects to ensure genetic disorders will not be passed down to the child. Preimplantation Genetic Diagnosis (PGD) genetic testing procedure entire process consists of multiple steps and the first part of the step is in-vitro fertilization (IVF), each step is performed by different fertility experts and laboratories. The process helps potential parents prevent the birth of a child with a serious genetic condition and the procedure for it is similar to that of in vitro fertilization, with an extra step added to check whether embryos are affected by a serious genetic condition.

Since 1989 preimplantation genetic diagnosis has been changing dynamically and new improved techniques have been introduced to it. Ideally, everyone who goes through IVF is recommended to undergo genetic testing, as a lot of money and time is invested to go through treatments, and having this test will help to increase your chances of a successful pregnancy. Realistically though, genetic testing is only permitted in special circumstances and is recommended when there is a family history of genetic disorders.

Who uses PGD?

The most common reason to use PGD is to avoid having a baby with a genetic disease. Preimplantation genetic diagnosis is recommended if couples are at risk of transmitting a known genetic abnormality to their children. It highlights three major groups of disease: sex-linked disorders, single gene defects, and chromosomal disorders. PGD is especially useful if one or both parents have a known genetic abnormality since it can prevent the disease from being transmitted to children. Those who might benefit most from this test are couples at increased risk for chromosome abnormalities for specific genetic disorders. Preimplantation genetic diagnosis is conducted with the intention to improve the chances of a normal pregnancy.

Indications for PGD

When there are recurrent miscarriages, family history of inherited disease, maternal age older than 38, one child already affected with a genetic disease, couples with multiple conventional IVF failures or ICSI failure, history of fetal aneuploidy in previous pregnancies, unexplained infertility, male factor infertility, family history of the structural chromosomal condition, family history of X- linked disease, severe monogenic diseases, etc. A single-gene disorder or monogenic disorders are the kinds of genetic disorders in human that arise from a mutation in a single gene, it is single-gene associated disorders.

Benefits of PGD

Doing preimplantation genetic diagnosis (PGD) allows couples the opportunity to have a child free of the genetic condition/ abnormality, as PGD is performed before pregnancy begins, thus eliminating unwanted risks of a child having a genetic condition. It increases the implantation success rate, reduces the possibility of having to choose to terminate the pregnancy following a diagnosis of a probable genetic disorder, also it can help eliminate some genetic diseases cures for which are not likely to be found soon, example: Tay- Sachs disease, cystic fibrosis, Huntington disease, X-linked dystrophies.

Different Types of PGD Available

PGD is a way for patients undergoing In Vitro Fertilization (IVF) to prevent a pregnancy affected by a genetic condition or chromosomal disorder and there are various types of PGD available, depending on the needs of the individual couple and the specific type of PGD should be discussed with your doctor. Single gene disorders, limited chromosomal screening, and comprehensive chromosomal screening (CCS) are the different types of preimplantation genetic diagnosis accessible. It can take several forms, depending on the couple’s needs.

Note: To perform a PGD, one should undergo IVF as the main treatment, as it is performed before embryo transfer during IVF treatment.

When is PGD done in an IVF Cycle?

On day five or day six, the biopsy for PGD is done on all appropriately developing embryos, the genetic material found in the cells from the embryos is tested for abnormalities and after considering many markers in the embryos tested, the medical and genetic team will decide the best possible embryo that can be taken forward for implantation.

One of the most significant uses for PGD is to identify and rule out embryos causing genetic problems in the pre-implantation stage itself. Some of the major genetic diseases that can be screened using PGD include cystic fibrosis, breast cancer, prostate cancer, muscular dystrophies, hemophilia, beta-thalassemia, amyotrophic lateral sclerosis.

It can be used to identify approximately 4,000 inherited single-gene disorders and is 98 percent accurate in identifying affected and unaffected embryos.

Note: Technological advances have made PGD safe, with hardly any risks associated. As long as you have an experienced embryologist and fertility clinic on your side.

PGD testing on day five 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.

The Cost of PGD and Legal Aspects

Preimplantation genetic diagnosis (PGD) cost varies depending on factors such as advanced female age, the method used for genetic testing, etc. The overall cost can vary from clinic to clinic, so patients are recommended to ask fertility clinics for providing them with a detailed cost estimate including all fees.  Since the PGD method is applied with the IVF ART technique, the cost of PGD includes both the procedure of preimplantation genetic diagnosis and the kit of IVF. It is widely used with IVF cycles today, 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.

Several Variables Involved in the Cost of PGD:

The cost of in vitro fertilization at the clinic, the cost of IVF medications, embryo biopsy procedure costs at the clinic, chromosomal and/or genetic analysis costs. PGD is a complex procedure that requires a lot of laboratory work, so the cost can be significant. It should be noted that there is no stringent law regarding preimplantation genetic diagnosis since this is performed before a pregnancy is established. In the USA, there are no federal or state laws that regulate the use of PGD, it is left to doctors’ discretion and the steps or procedure involved may differ from patient to patient on the basis of their treatment plan.

Is Genetic Testing Safe?

Genetic testing is a vital resource for many couples, especially those with known family histories of genetic defects, it helps by looking for specific markers for a certain disease that has a high probability of being passed down from parents to their offspring. Yes, it is safe and is recommended by doctors as a way to ensure that healthy embryos are used during fertility treatment. Preimplantation genetic diagnosis (PGD) does not affect the embryo’s viability, making this procedure a safe and recommended part of the IVF process.

How are embryos chosen for transfer?

Preimplantation genetic diagnosis results help to better identify the best embryos to transfer to the uterus to achieve a successful pregnancy. All decisions regarding which embryos to transfer to the uterus and how to use the remaining embryos are made together between the couple and their medical team. Embryos are created by combining eggs and sperm in the laboratory and from each embryo, one or two blastomeres are removed and tested. If the embryo is judged to be free of the disorder, they are then transferred to the uterine cavity.

Without PGD performed, embryos are chosen based only on their visual quality and morphology, which cannot distinguish chromosomally normal embryos from abnormal embryos. A preimplantation genetic diagnosis is a reproduction option that helps the couples to find out embryos carrying a genetic disease or chromosomal imbalance, thus avoiding the difficult choice of abortion.

Note: Genetic counseling is an important step to ensure that PGD is the right option for each couple.

Genetic counseling gives you information about how genetic conditions might affect you or your family. It is a communication process that seeks to help affected or at-risk individuals and families in understanding the natural history, disease risks, mode of transmission of a genetic disorder; to discuss options for risk management and family planning. Those who have decided to undergo IVF with a preimplantation genetic diagnosis will need to see a genetic counselor who is specialized in the procedure of PGD itself. Genetic counselors practice in several subspeciality areas of genetics including assisted reproduction technologies, infertility genetics, and prenatal diagnosis.

Preimplantation genetic diagnosis is a newly emerging form of early prenatal diagnosis that is performed on early embryos created by in vitro fertilization (test tube baby). Also, note that some people use PGD as a means to test gender, however, it is not only unethical, but it is also an offense. During your initial consultations, you will be asked to consider and decide on any potential tests you’d like to have completed on your developing embryos.

Concerns Regarding PGD

Preimplantation genetic diagnosis or PGD technique is not completely full-proof as it cannot completely eradicate the risk, also it is important to note that it is not the same as prenatal testing. Doing PGD does not make the need for prenatal testing redundant in the most serious cases. Also, there is a risk of all the embryos being chromosomally abnormal, meaning that transfer cannot take place, this means a cycle with no transfer, this may leave a significant emotional impact on patients and can be a difficult decision to take.

Our fertility specialist recommends doing the preimplantation genetic diagnosis to the couples that were transferred the best embryos but the pregnancy didn’t occur.

PGD and Surrogacy

PGD is the acronym for Preimplantation genetic diagnosis, sometimes also referred to as embryo screening. It can benefit all parties involved in gestational surrogacy (host surrogacy or full surrogacy) in this form of surrogacy, the child is not biologically related to the surrogate.

One of the benefits is identifying embryos that stand a better chance of survival, increasing the potential for a full-term pregnancy. Proceeding with PGD testing will help the surrogacy agency/ fertility clinic match intended parents with a surrogate who shares the same beliefs about ethically sensitive topics, as PGD testing will also open the doors for intended parents and the surrogate mother to discuss, if, or when, terminating the fetus would be acceptable.

Bear in mind that PGD testing is still relatively new and not a perfect science, while it may contribute to an increased chance of a successful pregnancy and healthy child, it is not a guarantee. Make sure to find a fertility clinic with high success rates and large client numbers, talk to them to learn about their experiences and success stories, as well as any challenges or limitations they have faced.

For intended parents who want to make sure that their baby receives the best possible chance of having a healthy life, considering preimplantation genetic diagnosis is 100% worth it, as the last thing any parent wants is to pass on a genetic mutation that can negatively impact their child’s life. Some genetic mutations can cause surrogates to miscarry, so it’s worth it to save time as well.

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