Due to the progress in reproductive medicine, it is now possible to solve the infertility problem. For many couples, IVF has become a real chance to fulfill a cherished dream and become parents. However, when choosing this treatment method, it is essential to consider all the possible pitfalls and weigh the pros and cons. In turn, PGD (preimplantation genetic diagnosis) helps to increase the efficiency of IVF and the probability of a successful pregnancy. Such testing allows you to avoid transmitting a genetic disease to your child, reducing the risk of not carrying a pregnancy.
How is PGD conducted? Who needs this test? What pros and cons of preimplantation genetic diagnosis should be taken into consideration when choosing a PGD? Future parents can find the answers to these questions in this article.
What Is Preimplantation Genetic Diagnosis (PGD)?
The PGD method of gene therapy was developed to prevent possible genetic abnormalities in early embryonic development. A healthy embryo is also called an euploid embryo. It contains 46 chromosomes, 23 of which come from the egg and another 23 from the sperm.
An aneuploid embryo has a higher number or lack of chromosomes. This can lead to problems with implantation or carrying the fetus and increase the risk of miscarriage. But, if the pregnancy is successful, the newborn child can have physical or mental disabilities. Timely testing will help to detect an aneuploid embryo early and avoid problems in the future.
In addition to these two types of embryos, mosaic embryos have also been recently identified. Such embryos contain two or more cell lines with different numbers of chromosomes (e.g., some cells are euploid, and others are aneuploid).
Possible reasons for PGD
- A couple in which one or both partners are carriers of a genetic disease.
- If either partner has an altered karyotype, i.e., an abnormality in the number of chromosomes.
- Age of the partners. The older the future parents are, the higher the risk of their child having genetic disorders.
- If the couple has an experience of failed IVF attempts.
- The woman has repeated cases of miscarriages.
- The presence of hereditary genetic diseases in the family of one or both partners.
Steps of PGD
One of the main advantages of PGD is that it takes place before artificial insemination. Thus, only healthy, high-quality embryos are selected for transfer. The procedure itself consists of several steps and takes several days to complete.
After the egg is picked up and assessed in the laboratory, fertilization is performed. This can be done by using the usual method of fertilization when sperm and eggs are placed in a cup for cultivation. But ICSI is the most common method used for PGD. With this method, each individual sperm cell is injected into an egg cell.
We take a few days for the embryo to grow. There are two approaches:
- In the first case, the embryo develops for 3 days. During this time 6-8 cells manage to form.
- In the second, the process lasts for 5-6 days. After 6 days, the blastocyst develops. At this stage, the embryo already consists of 100-150 blastomeres. They are divided into two groups. One part of the cells will take part directly in the fetus development, while the second group (trophoectoderm) will be a source for the placenta.
When the embryo is fully developed, a biopsy is performed. A few cells are extracted through a small hole in the zona pellucida. This step can vary depending on how long the embryo has been growing.
On the third day of embryo development, one or two cells are taken for the test. On day 5-6, a specialist in the laboratory takes a small set of cells from the trophectoderm. This approach is less traumatic for the embryo and is also more effective. At the same time, these cells must be uninucleate (having a single gene where DNA is stored). Otherwise, there is a risk of distorting the results.
This involves the delicate storage of the obtained cells in a special vessel prior to direct testing.
Using molecular biological techniques such as PCR, FISH, CGH array, or NGS, specialists examine the obtained cells. This step can take one to two weeks. This analysis will reveal possible chromosomal abnormalities in the cells and exclude such embryos.
What Are the Pros and Cons of Preimplantation Genetic Diagnosis
As you can see from the description, preimplantation genetic diagnosis is a fairly complex process. This method can help expectant parents prevent a variety of complications. But is this kind of genetic testing suitable for everyone? The right decision can only be made after a comprehensive study of the PGD testing pros and cons.
Pros of PGD
Preimplantation genetic diagnosis can help you achieve such benefits from the reproductive treatment process:
Detecting wide range of diseases
With PGD, you will not detect all possible fetal abnormalities, but this test can reveal many dangerous diseases. You can check if the embryo is prone to Muscular dystrophy, Cystic fibrosis, Hemophilia, Fragile-X, Tay-Sachs, Sickle-cell anemia.
Transfer of euploid embryos only
PGD allows early detection of abnormal embryo formation and thus eliminates diseases of the future child.
Increase the successful implantation and pregnancy rate
One of the essential aspects of preimplantation genetic diagnosis pros and cons is that this test allows us to determine whether the embryo is healthy and suitable for implantation. Thus, the most viable embryos are selected. As a result, the possibility of a successful pregnancy and a healthy child is increased.
Reduced abortion rate
One of the benefits of preimplantation genetic diagnosis is the possibility to define the genetic status of the embryo before starting pregnancy and the subsequent need for abortion in case of unfavorable results.
At this stage of embryo development, it has totipotent stem cells. This means that these cells are actively dividing until the human body is formed. Therefore, taking a couple of them from the embryo will not affect the development of the future child’s organism.
Cons of PGD
Although the effectiveness of this method is quite high, intended parents should also consider the preimplantation genetic diagnosis risks.
Risk of damage to the embryo
Such testing involves some manipulation of the embryo. Because it will be outside the incubator for some time, some of its common features may change. This can cause it to stop growing. Pregnancy will not be gained in a case like this. This problem can occur even with healthy embryos without any abnormalities. But it is worth noting that the probability of such damage is very low. But still, couples who agree to do PGD should be aware of this risk.
Possibility of undetected disease
PGD has a very high success rate and really helps to reduce diseases. But speaking about the disadvantages of PGD, it is essential to remember that, like all other tests, it does not always guarantee 100% accuracy. Therefore, there is still some probability of not detecting the issue. But this risk is very low compared to how often the PGD helps reduce the possibility of different disorders.
For some people, weighing all the PGD pros and cons is very important because this kind of testing can be emotionally challenging. After all, if the result is positive, the embryo transfer will have to be canceled.
StartYourSurrogacy.com is a team of skilled professionals with years of experience in reproductive medicine. Our main goal is to provide you with the highest quality service. Our clinic can provide you with all the services associated with the reproductive program, including the selection of a sperm and egg donor, all the necessary testing, observation of the surrogate during pregnancy and childbirth.
IVF is a serious and responsible step for future parents. There are usually a lot of emotions, stress and fears associated with this process. No one can guarantee you a 100% successful result. But with the help of a PGD, a couple can exclude some risks and reduce IVF time and expenses.
StartYourSurrogacy.com specialists will give you the comprehensive information you need and tell you if PGD testing is necessary in your case. You can also discuss with them all the advantages and disadvantages of PGD.