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SAFE FERTILITY CENTER

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Genetic Testing

Genetic testing

I. Overview of PGD

A. Preimplantation Genetic Diagnosis (PGD) for aneuploidy screening
Preimplantation genetic diagnosis is scientific technique, which is developed to test the embryos for specific diseases or screening of chromosome abnormalities. In IVF, 30 – 70% of embryos have chromosomal aneuploidy. PGD can be used to improve the success rate for infertile couples, by selection of the most suitable embryos to transfer.
The most recent PGD technology for comprehensive chromosome screening is Next Generation Sequencing (NGS). Safe Fertility Center is proud to be the first IVF clinic in Thailand offering the NGS technique.

Safe Fertility Center offers the PGD services for :

  • Comprehensive chromosome screening (CCS) by using aCGH or NGS
  • Single gene disorder
  • Structural chromosome abnormalities, for example: chromosomal translocation

*Safe Fertility Center stops a service of PGD-FISH technique

B. How is PGD accomplished?

The biopsy process  By using advanced blastocyst culture technology, the embryos, which reach the blastocyst stage on the fifth and sixth day of development, are biopsied. Three to five trophectoderm cells, that will be destined to be the placenta, are removed and analyzed for genetic condition.

Trophectoderm biopsy has less negative impact to the embryos when compared with day-3 biopsy.
Cleavage stage biopsy (on day 3 of development) is recommended in couples who are poor responders, poor embryo development in previous IVF cycle, and in couples who want to undergo fresh embryo transfer.
Genetic analysis   The genetic laboratory at Safe Fertility Center can use various techniques to analyze the cells according to the specific genetic problems. In case of aneuploidy screening, NGS is used to check all 23 pairs of chromosome, including chromosome X and Y, with the higher resolution data. In case that the couples have structural chromosome abnormalities, such as Robertsonian or Reciprocal translocation, aCGH is used to check the unbalanced translocation as well as errors of all other chromosomes in the embryos.

If the couples have a problem of single gene disorders, patient-specific PGD test will be developed by Safe Fertility Center’s genetic team. The DNA copy numbers are increased by polymerase chain reaction (PCR) based method, then the PGD can be done to identify which embryos carry that mutant gene or not.

C. Risk of the procedure
There are many scientific studies shown that the implantation rate and ongoing pregnancy rate are improved with PGD for comprehensive chromosome screening. The success rate of single embryo transfer to achieve single live birth healthy baby is also improved by using this technique. Because the embryos, which are found to be genetically normal have overall better chance to implant and develop to live birth pregnancy. However, no one can guarantee that the embryo will implant into the womb after transfer.

The biopsy procedure does not cause any structural abnormalities or handicap to the baby. Safe Fertility Center has highly experienced embryologist, so the embryos could be less traumatized by this procedure.

II. Comprehensive chromosome screening : aCGH / NGS – 1st available in Thailand

Safe Fertility Center is the first IVF center offering Next Generation Sequencing (NGS) technology in Thailand. NGS is the significantly advanced technique that consumes less time and provides more accurate results in the purpose of PGD.

For comprehensive chromosome screening (CCS), all 23 pairs of chromosome, including X and Y chromosomes, as well as some structural chromosome abnormalities, can be checked. Transferring of genetically normal embryos will help to increase the success rate of the IVF treatment, especially in the couples with advanced age, recurrent implantation failure, unexplained recurrent miscarriage, etc.
CCS can be done by using array Comparative Genomic Hybridization (aCGH) and NGS. PGD for structural chromosome abnormalities, such as Reciprocal or Robertsonian translocation, is able to be detected simultaneously with other chromosome errors by using this technique.

a. How to undergo IVF and PGD-NGS or aCGH?

  • After embryos are created in IVF cycle, they are cultured in the incubator. Assisted hatching is done on day 3 to create the hole on the embryo shell (zona pellucida). When they reach the blastocyst stage on the fifth and sixth day of development, trophectoderm biopsy is done to remove 3 – 5 cells for analysis. All biopsied embryos are frozen immediately after biopsy.
  • Cleavage stage biopsy (on day 3 of development) is recommended in couples who are poor responders, poor embryo development in previous IVF cycle, and in couples who want to undergo fresh embryo transfer.
  • For PGD-NGS, DNAs from the sample cells are extracted, amplified, and analyzed by comparing with the reference human DNA. The gain and/or loss of the DNAs are identified using microarray by 3 highly experienced scientists. Safe Fertility Center’s genetic laboratory uses the VeriSeq PGS solution, consisting of the VeriSeq PGS Kit – MiSeq and the MiSeq System for NGS test. NGS has more advantage than aCGH – higher resolution can detect the small chromosome errors, so it can reduce the false negative, and mosaicism can be easily detected.
  • For PGD-aCGH, after extraction and amplification of DNAs, analysis is done by using 24SURE aCGH.

b. Is the result reliable?
As the other scientific test, there is a very small risk of abnormal results (false positive/false negative). The reliability is 97.5% for NGS and 95% for aCGH. Prenatal testing might be considered for the abnormalities that may occur from other conditions.

c. Risk of the NGS/aCGH test

  • The results can be achieved in 95% of the tested embryos.
  • 7% of the PGD cycles end up with no suitable embryos for transfer (all embryos are abnormal).
  • Risk of the IVF and biopsy process : please refer to patient information and overview for PGD

III. Single gene disease

Single gene disease is a hereditary disease caused by a mutant allele of a single gene, e.g. alpha or beta-thalassemia, spinal muscular atrophy, duchenne muscular dystrophy, cystic fibrosis, etc.

a. How I can undergo PGD for single gene disorder to avoid the affected child?

  • Couples who are at risk to have child with single gene disease are mostly not infertile. Before undergoing PGD-single gene disorder, investigation for disease-causing mutation, genetic and IVF counseling are mandatory for specific-PGD lab setup.
  • Ovarian stimulation, egg retrieval and sperm collection, ICSI will be done. The embryo will be cultured to reach the blastocyst stage on the fifth and sixth day of development. Three to five trophectoderm cells, that will be destined to be the placenta, are removed and analyzed for genetic evaluation. In case of day 3 biopsy, 2 blastmeres will be removed for PGD-single gene disease. The biopsied embryos will be frozen immediately after biopsy.
  • After extraction and amplification of the DNAs from sample cells, the amount of DNAs is increased by polymerase chain reaction technique (PCR). The specific part of amplified DNA samples will be checked with pre-set up PGD-lab to identify the mutant DNAs.
  • The unaffected embryos will be transferred to the womb in the frozen-thawed cycle.

b. Is the result of PGD-single gene disorder reliable?
The reliability of the test is 95%. However, prenatal diagnosis for such disease is strongly recommended.

c. Risk of the PGD-single gene disease

  • The results can be achieved in 95% of the tested embryos.
  • 10-15% of the PGD cycles end up with no suitable embryos for transfer : all embryos carries the mutant genes or embryos without mutant genes may have other unrelated chromosomal errors.
  • Risk of the IVF and biopsy process : please refer to patient information and overview for PGD