pgd

WHAT IS PREIMPLANTATON GENETIC DIAGNOSIS [PGD] ?

In IVF, preimplantation genetic diagnosis  [PGD] is a process establishing whether embryos are genetically healthy or not. Preimplantation genetic diagnosis [PGD] is a procedure used prior to implantation to help identify genetic defects. 

 

 
Preimplantation genetic diagnosis (PGD) process involves the use of assisted reproductive technology [ART]. It is a method which involves the examination of the embryos which once fertilized the embryos are developed for 5-6 days after IVF or ICSI and if suitable for the procedure, doing a biopsy on those embryos by extracting one or two cells. It is used to examine the embryos in terms of chromosome structure and numbers before transplanting them in to the mother’s womb. The aim of PGD is to make sure that the healthiest embryos are chosen by analyzing chromosome anomalies.
 
PGD is a technique that enables couples with a particular inherited condition in their family to avoid passing it on to their children. The process helps potential parents prevent the birth of a child with a serious genetic condition. PGD is used when a couple has a known risk of passing on a genetic abnormality and diagnostic testing is performed on an embryo to determine if it has also inherited the abnormality.

The genetic material (DNA or chromosomes) within these cells of the embryo is then tested for the genetic or chromosomal abnormality. An unaffected embryo is then transferred to the woman’s uterus to implant. This serves to prevent certain genetic diseases or disorders from being passed on to the child. If successful, the procedure will result in pregnancy and the child should not be affected by the condition for which it was tested.  

Fertilized eggs (after ovum pick up and fertilization by sperm) start to produce the first two celled embryos at the end of the first day and these start, rapidly, to increase cell numbers by cleavage (cell division), blastomere. As a result of fertilization an excess cell called “polar body” emerges. At the end of the fifth day, within the embryos whose number of cells have increased there starts to build up structures full of fluid and these cells are called “blastocysts”. Of those cells, whose number increases by division, some will develop into the fetus (baby) while some others start building up the layer called trophectoderm which will constitute the placenta that will be responsible for the nutrition of the baby. PGD is done by examining genetic material of the cells extracte by biopsy from the polar body, blastomere or trophectoderm.

In order to determine genetic diseases and to select HLA matched embryos PGD is done via PCR analysis of the biopsy cells on the third or fifth day of embryo development. DNA material in each cell extracted via PCR is duplicated. On the third day of fertilization, embros have only 6-8 cells (blastomere) and at this time, only one cell can be extracted from the embryo and PCR be applied. However, on the fifth day, the embryo reaches the blastocyst stage and more cells can be extracted from trophectoderm and more reliable results can be obtained by PCR.

PGD brief:

  • * In ideal cases increases the chances for the success of IVF
  • * Increases the chances of pregnancy.
  • * Decreases the risk of miscarriage.
  • * Decreases the risk of terminating the pregnancy for medical reasons.
  • * Decreases the chances of multiple pregnancies.
  • * Reduces the amount of economical and psychological load on couples due to repeated 
  •   unsuccessful IVF treatments.
  • *Provides the family with a chance to select sex.
 
Which conditions can be diagnosed using preimplantation genetic diagnosis [PGD]?

PGD is available for three broad categories of conditions including:

Single gene defects for which PGD testing is available.

Chromosomal abnormalities, including inversions, deletions, aneuploidy (an abnormal number of chromosomes), and translocations (where a piece of one chromosome either becomes attached to another chromosome or swaps places with a segment from another chromosome).

Sex-linked conditions, for which it is not yet possible to test for the specific genetic mutation, in which case they test for sex rather than mutation.

Who can use preimplantation genetic diagnosis [PGD]? 

Couples who request PGD are at risk of passing on a serious genetic condition to their children. Parents may have the condition themselves or be carriers of the condition. They may already have a child affected or they may have experienced the loss of a child or pregnancy affected with the condition.

Couples generally considered for PGD include:

Carriers of a serious* autosomal recessive condition: For carriers of an autosomal recessive condition, there is a 1 in 4 (25%) risk of each pregnancy delivering an affected child.

Carriers of a serious autosomal dominant condition: For carriers of an autosomal dominant condition, there is a 1 in 2 (50%) risk of each pregnancy delivering an affected child.

Couples with inherited chromosome disorders. 

Couples with a family history of serious sex-linked disorders: Couples with a family history of a sex-linked disorder have a 1 in 4 (25%) risk of each pregnancy delivering an affected child (half of all male children).

Preimplantation genetic diagnosis [PGD] may be recommended if:

  • you or your partner has a family history of a serious genetic condition and/or
  • you and your partner already have a child with a serious genetic condition and/or
  • you and your partner have had a number of pregnancy terminations because your baby had a serious genetic condition.

Who should consider having preimplantation genetic diagnosis [PGD]?

  • Candidate mothers of 36 and higher years of age
  • Couples who have tried IVF treatment at least twice but couldn’t get pregnant
  • Couples who have experienced concurrent miscarriages [except for translocation  carriers
  • Couples (one of) who(m) are balanced translocation carriers
  • Partners who have a family history and risk of single gene diseases such as thalassemia
  • [Mediterranean anemia], sickle cell anemia, cystic fibrosis and SMA
  • To choose HLA matching embryos
  • Couples who have had children with genetic disorders previously
  • Mothers with a pregnancy history of aneuploidy (chromosome defects)
  • In gonadal mosaicism cases (couples having normal genetic test results although they’ve had two or more cases of anomalies regarding the offspring)
  • TESE cases [cases with advanced male infertility]
  • Poor responders (in cases when response to hyperstimulation procedure is insufficient)
  • In cases regarding transcendency related to the X chromosome, if the disease cannot be diagnosed genetically, then sex selection.

How safe are embryo biopsy and PGD?

In order to do Preimplantation genetic diagnosis [PGD]cell samples from every embryo should be taken. Chances of damaging the embryos during PGD is almost zero and the rate of reported damage is stated as 0.3%.

How reliable are the results of PGD?

Although they may vary depending on the method used, the chances of error are about 2-7%.

What does “single cell diseases” mean?

When the structure of units encoded in our DNA called genes are altered or broken, this leads to a group of genetic diseases called single cell disorders. Such genetic diseases are more common in cousin/relative marriages.

The preimplantation genetic diagnosis [PGD]of single cell disorders relies on the DNA analysis of one cell. Preimplantation genetic diagnosis (PGD) applies to cystic fibrosis, Hemophilia A1 and B, Kistik fibrosis, Hemofili A1 ve B, Alpha 1-antitrypsin deficiency, Tay-Sachs disease and Sickle cell anemia, Retinitis pigmentosa, Thalassemia (mediterranean anemia), Alport syndrome, Gaucher’s disease, Long-Chain Acyl CoA Dehydrogenase Deficiency, multiple epiphyseal dysplasia, achondroplasia (dwarfism), Neurofibromatosis, epidermolysis bullosa, Myotonic dystrophy, X-linked hydrocephalus, cancer predisposition and Fanconi anemia.

As the technology advances, Gender Selection is to determine the gender of the baby by studying on the cell taken by biopsy method (PGD), from the embryos (fertilized eggs) obtained by in-vitro fertilization treatment.

Gender selection has been legally realized in Northern Cyprus for almost 15 years. Since gender selection has not been legal globally, especially in European countries, many families prefer our center for gender selection. Couples willing for gender selection in many cases are able to conceive via natural process, in order to obtain a normal embryo, in-vitro fertilization treatment must begin. Preimplantation genetic diagnosis [PGD] operation is realized, subsequent to normal IVF process by a genetic test implemented during development of embryos (fertilized eggs).

Processes to be applied during preimplantation genetic diagnosis [PGD] treatment:

  • 1- Primarily, egg multiplication process [ovulation induction] should be implemented in exactly the same way in in-vitro fertilization,
  • 2- When the eggs reach a specific dimension, egg collection processes will be realized with a slight anaesthesia,
  • 3- Embryos are obtained with sperm sample taken from the spouse,
  • 4- Embryos will be developed within laboratory environment for 3 days,
  • 5- On the 3rd day, genetic screening will be realized on embryos by extracting 1 or 2 cells. As numeric anomalies in chromosomes will be examined by FISH (Fluorescent in-situ Hybridization) technique, and PCR (polymerase chain reaction) is used for single genetic disorders.
  • 6- Healthy and desired gender embryos will be transferred into candidate mother on the 5th day.
  • 7- After 12 days, pregnancy test will be realized to determine whether the candidate mother is pregnant.

Gender selection is an in-vitro fertilization application which has a high chance of pregnancy especially in young patients (over 35 age) due to number and quality of eggs. In pregnancies obtained after treatment, babies being healthy and accuracy rate of its gender is 99.9 percent.
Pregnancy success rate after gender selection treatment differs depending on patient’s age, egg reserves, how many embryos will be healthy and at the same time has the gender desired by family.

Why Northern Cyprus?

  • Gender selection is legal in Northern Cyprus.
  • The price of gender selection operation is much more advantageous comparing to other countries.
  • Experience and knowledge in gender selection is fast achieving escalating figures.
  • Holiday opportunities, in a country where the benefits of the crystal clear sea, mild all year round climate, relaxed island lifestyle and the sun always shines.
  • Most important of all, special care and treatment provided by our high quality and modern IVF center under supervision of Op. Dr. Tolga TUNA.

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CYPRUS IVF CLINIC
Fevzi Çakmak Sok. Kurtuluş Cad.
Kyrenia - North Cyprus

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