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Preimplantation Genetic Diagnosis

 

Preimplantation Genetic Diagnosis

 

Preimplantation genetic diagnosis (PGD) is a reproductive technology that tests the chromosomes and genes of the embryos used in an intracytoplasmic sperm injection (ICSI), and can diagnose for the presence of genetic anomalies, or aneuploidy.  Chromosomes and genes with no anomalies are known as euploidy. 
Prenatal diagnosis is performed by use of amniotic fluid test and ultrasound to diagnose the presence of anomalies of the baby before it is born.  Since this test will be done after pregnancy, if it is found to have aneuploidy, the patient will be forced to make the tough decision as to have or abort the pregnancy. 
In PGD, it is known whether there are any chromosomal anomalies in the embryo and because of this one can choose the embryo that has a low possibility of ending up as a miscarriage or still born before the embryo is returned to the uterus (embryo transfer). 
Presently in Japan, under the guidelines of the Japanese Society of Obstetrics and Gynecology, PGD is approved and carried out on those patients with severe hereditary disease(s).

 

PGD Target & Genotype

  • 1. Duchenne Muscular Dystrophy (DMD): X-linked – deleted form, micro-mutant
  • 2. Myotomic Dystrophy: Autosomal dominance – Abnormal elongation of repeat sequences
  • 3. Leigh Syndrome: Mitochondrial disease – Variants of mitochondrial DNA
  • 4. Adrenoleukalodystrophy: X-linked - Variants
  • 5. Ornithine transcarbamylase deficiency: X-linked - Variants
  • 6. Habit ual miscarriage of balanced translocation carrier

 

The screening test called “preimplantation genetic screening (PGS)”, uses the same technology as preimplantation genetic diagnosis (PGD).  Preimplantation genetic diagnosis (PGD) is targeted to couples with severe hereditary disease and the purpose is to check for aneuploidy of chromosomes and specific genes of the embryo, whereas preimplantation genetic screening (PGS), the purpose is to reduce miscarriages that occur caused by the aneuploidy of other chromosomes and genes.  It is proven that the miscarriage rate decreases significantly just by taking a preimplantation genetic diagnosis.  PGD was developed to decrease the physical and mental burden by testing for the presence of anomalies in the embryo before pregnancy is achieved.

 

Overseas, preimplantation genetic screening has been implemented in many countries such as the United Kingdom, the United States, France, Scandinavia, Russia, Turkey, Argentina, Taiwan, Korea, India, Thailand and China.  In Japan, according to the guidelines of the Japanese Society of Obstetrics and Gynecology, PGS testing is not authorized.  However, in February of 2015, the Society approved a 3-year clinical research plan, and a possibility has arisen that PGS could be used in fertility treatment soon.

 

In cases of embryos being aneuploidy, it is unlikely to implant, or even if it does implant it may be miscarried or lead to a still birth.  Even within the chromosomal anomalies, it is understood that there are many trisomies from the karyotype analysis of miscarried fetuses.  Additionally, in the chromosomal anomaly called, “reciprocal translocation”, which is one of the causes of habitual miscarriage, there is only about 17% of embryos resulting in birth.  Generally speaking for habitual miscarriage patients the miscarriage rate is said to be about 80-90%, but if preimplantation genetic screening is performed, there are studies being done by American labs showing the implantation rate will improve.

 

If miscarriages are repeated, uterine scarring occurs increasing the possibility for uterine adhesion.  When uterine adhesion occurs, problems with pregnancy and birth will easily occur such as interference with implantation thus leading to infertility, possibility of miscarriage will become high, and a cause of heavy bleeding by the adhesive placenta during delivery. 
As for PGD and PGS, by means of reducing miscarriages it will prevent uterine adhesion and is also considered to be a technology that can decrease the difficulties in pregnancy and during the time of birth.

 

 

Chromosomal anomalies seen with miscarriage

Chromosomal anomalies seen with miscarriage

Maribel Grande : Human Reproduction Vol.0 no.0 pp.1-9,2012 was used as the original and made at Oak Medical Group.

Detected image of trisomy by means of the FISH method

Detected image of trisomy by means of the FISH method

Anver Kulviev, Svetlana Rechitsky and Oleg Verlinsky : ATLAS OF PREIMPLANTATION GENETIC DIAGNOSIS THIRD EDITION :
CRC Press


We are providing the general information about Preimplantation Genetic Diagnosis.
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