It is fascinating that through genetic science, it is possible to closely determine the health and the gender of the fetus, even before it is transferred to the mother’s womb.

Using PGD and PGS methods, it can be checked whether the fetus has serious genetic defects or not. Some genetic defects are major and are caused by changes in a person’s number of chromosomes. This type of disorder is called an aneuploidy, a chromosomal disorder in which there are missing or extra chromosomes. In trisomy, there is an extra chromosome, and in monosomy, one chromosome is missing. In some cases, inherited disorders are caused by another mutation in the genes. These disorders can include diseases such as thalassemia, sickle cell, cystic fibrosis, metabolic diseases, blindness, deafness, typhoid and many others. In most cases, both parents must have the same copy of the defective gene and pass it on to their child in order to have an affected child.

PGD ​​is a test used to genetically evaluate the fetus before it is transferred to the uterus and even to determine the sex of the fetus. The purpose of these experiments is to investigate single gene and chromosomal abnormalities in the fetus before implantation.

Of course, with this method, it is possible to perform an egg test before fertilization and select the sex of the fetus. A type of PGD is used for pre-implantation genetic diagnosis of large chromosomal defects, which is an extensive test used to diagnose aneuploidy on all chromosomes, including autosomal chromosomes as well as X and Y sex chromosomes.

Usually, pre-implantation genetic diagnosis (PGD) may be suggested to couples who use in vitro fertilization (IVF) to conceive. This is especially important for couples who have a family background of genetic abnormalities or are at risk of having a child with genetic or chromosomal disorder. In such cases, the health of the fetus is checked and screened for certain genetic disorders and mutations before transferring the fetus to the uterus.

What diseases are PGD and PGS used to diagnose?

Some of the genetic diseases that are examined by pre-implantation genetic diagnostic and screening methods are:

• Down syndrome

• Thiosx disease

• Cystic fibrosis

• Turner syndrome

• Edward Syndrome

• Klein-Felter syndrome

• Thalassemia

• X-linked diseases such as hemophilia and muscular dystrophy

• Muscular and Spinal Atrophy

Who is PGD and PGS used for?

In general, the five main groups of patients for whom PGD and PGS are used, include:

• Patients using IVF, where the age of the female party is over 38

• Patients of any age group who have had consecutive IVF failures

• For screening hereditary  genetic diseases

• Patients with potential for passing chromosomal mutations

• Patients afflicted by recurrent abortions

What is the difference between PGS and PGD?

Both of these genetic evaluation technologies require IVF to be performed but differ in their manner of execution. Both of these treatments are different in terms of application method. Although, they do not guarantee a healthy delivery, they can be helpful for those couples who are trying to conceive without success. You can decide if the PGS and PGD methods are suitable for your situation while performing IVF. But before that, you need to study these methods, their effects and costs as well as the risks associated with each of these technologies thoroughly in order to fully familiarize yourself with their ups and downs.

What is Preimplantation Genetic Screening (PGS)?

Preimplantation genetic screening (PGS) does not look for specific genes, but examines the overall chromosomal arrangement of the fetus. Embryos are classified into two types, euploid and aneuploid. Under normal conditions, eggs and sperm each carry 23 chromosomes and share them in the fertilization process. Combining and fertilizing them together creates a healthy embryo with 46 chromosomes. This achievement is called a euploid fetus. In some cases, if the fetus has an extra chromosome or loses one, it is called an aneuploidy.

In most cases, aneuploid fetuses are unable to implant in the uterus and abort. In exceptional circumstances, these fetuses may continue to live, the pregnancy may continue, and they may end up in labor. In this case, the newborn may have a mental or physical disability. Down syndrome is an example of an aneuploidy with an extra chromosome.

Pre-implantation genetic screening, or PGS, can be helpful in detecting such problems before transferring the fetus to the uterus. Pre-implantation genetic screenings can also determine the genetic sex of the fetus from the beginning. Comprehensive Chromosome Screening (CCS) is a technique used in the pre-implantation genetic screening (PGS) method to determine if the fetal chromosome arrangement is XY (male) or XX (female). This is done to prevent the transmission of any sex-related diseases or to balance the family.

Who is recommended for pre-implantation genetic screening (PGS)?

Pre-implantation genetic screening (PGS) is recommended for parents who do not have a history of known genetic abnormalities. This method is also recommended for couples who meet the following criteria:

• People who want to know and select the gender of their child

• Cases where the woman is over 38 years old.

• Couples who are interested in transferring only one fetus to the uterus.

• Couples with a history of miscarriage.

• Couples who have a history of failure in IVF treatment or a failed implantation experience

What are the reasons for using pre-implantation genetic screening (PGS)?

Some of the more common reasons for using pre-implantation genetic screening (PGS) in the treatment of infertility are described below.

• This procedure may improve the chances of success for an embryo transfer:

By selecting a single selected embryo, doctors will only transfer one healthy embryo to the uterus via IVF. This increases the chances of pregnancy, reduces the risk of miscarriage, and reduces the risk of twin or multiple pregnancies, which can be dangerous for the mother and her unborn children.

• Identifying the child’s gender:

Pre-implantation genetic screening (PGS) can help determine the sex of the baby. As a result, reduce the risk of transmitting sexrelated genetic diseases. In addition, many couples today use this method to choose the sex of their child.

• May help reduce the risk of miscarriage:

Miscarriage is common in 25% of pregnancies. Repeated abortions (three times in a row) are not a good sign. Repeated miscarriages can be harmful to a mother’s physical and mental health and also reduce the chance of future pregnancies. Pre-implantation genetic screening (PGS) helps reduce the risk of miscarriage.

• Increased chances of pregnancy through IVF:

In order to increase the chances of pregnancy in cases where the male party is infertile or the female party is rather old as well cases where several IVF cycles have proved futile, reproductive doctors recommend pre-implantation genetic screening alongside IVF. Although there are clinics that based on their protocols, perform a mandatory pre-implantation genetic screening procedure for all their patients.

What is PGD for Sex Selection?

By identifying the genetic content of the embryos before implantation, their sex can be determined. By using PGD, and by selecting fetuses with the desired sex of the family, it is possible to help maintain the balance of the family in terms of gender through having a child of the desired sex (male or female).