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PGT-A / PGT-M

Preimplantation Genetic Testing for Aneuploidy (PGT-A)/
Preimplantation Genetic Testing for Monogenic disorders (PGT-M)

 

Preimplantation Genetic Testing for Aneuploidy (PGT-A)

Before the embryo is implanted, the chromosome examination of the embryo is performed to detect whether the number of 23 chromosomes is abnormal, whether there is deletion of large fragments (≧10Mb), or unbalanced translocation. Embryos with normal chromosomes are implanted to increase the pregnancy rate and reduce the miscarriage rate.

Recommended for:

  • Females with advanced maternal age 38 years old and above
  • Those who have miscarried more than two times
  • Those who experienced repeated failure with assisted reproduction
  • Those with a family history of chromosomal abnormalities or chromosomal translocations.
  • Those who want to avoid fetal chromosomal abnormalities

Limitations of this procedure:
The primary examination of PGT-A is the normalcy of the chromosome number. It cannot be used to detect single gene defect diseases such as thalassemias, muscular dystrophies, hemophilias, etc. This procedure cannot detect genetic changes of < 10Mb fragments, chromosomal recombinations, chromosomal inversions, balanced transpositions, uniparental disomy (UPD), polyploidy, haploidy, low grade chromosomal mosaicism. Hence, depending on personal conditions, a chorionic villus sampling or amniocentesis may still be recommended after a successful pregnancy with PGT-A.

Approach to PGT-A:

  • Start enquiry at our infertility clinic for proper consultation and assessment
  • Patients are advised to call our reproductive health center 3 days before menstruation for the start of IVF treatment
  • Egg retrieval is done on about Day 14 of the menstrual cycle and a consent is signed for PGT-A at the same time
  • Eggs are fertilized by sperm using ICSI.
  • After culturing the embryos for 5-6 days until blastocyst stage, a few cells are removed from the outer layer of the embryo (this is called a trophectoderm biopsy). The embryos are frozen immediately using vitrification.
  • The biopsy specimen is then sent for Preimplantation Genetic Testing for Aneuploidy (PGT-A) / Next Generation Sequencing (NGS). It takes about 10 days to have the result

Preimplantation Genetic Testing for Monogenic disorders (PGT-M)

Preimplantation Genetic Testing for Monogenic disorders is a technology to help couples who may have serious genetic conditions that may be passed on to their children. Couples who have dominant or recessive single gene defects will have a 1 in 2 (50%) or 1 in 4 (25%) risk of delivering an affected child for each pregnancy. Examples of such conditions are thalassemia, muscular dystrophies, hemophilia, and ankylosing spondylitis. To avoid passing on these defective genes to the next generation, what can be done is to first collect blood samples from the family, and have our molecular genetics laboratory identify the defective locus, design a customized gene probe, and set about on a genetic diagnosis on the embryos. After which, embryos that are free of the genetic disease are chosen for transfer to the prospective mother's uterus.

Limitations of this procedure:
The aim of PGT-M is to select embryos free of known genetic disease for transfer to the maternal uterus. For other undetected genetic mutations, non-familial inherited diseases, chromosome deletions, abnormalities in chromosome sets, etc., patients are advised to undergo chorionic villus sampling or amniocentesis for successful pregnancies after PGT-M.

Approach to PGT-M:

  • Start enquiry at our infertility clinic for proper consultation and assessment.
  • Patients will provide the family genetic history together with a confirmed diagnosis of the genetic disease.
  • Couples and their relatives are sent to the molecular genetic laboratory for blood sampling and genetic probe design (approximately 1 month).
  • Visit our center to sign consent for the PGT-M and pay the fee for the probe design.
  • After completion of the probe, patients will be informed and advised to call our reproductive health center 3 days before menstruation for the start of IVF treatment.
  • Egg retrieval is done on about the day 14 of the menstrual cycle.
  • Eggs are fertilized by sperm using ICSI.
  • After culturing the embryos for 5-6 days until blastocyst stage, embryo biopsy will be done and a few cells that would eventually become placental cells are removed from the outer layer of embryo（this calls a trophectoderm biopsy). The embryos are frozen immediately using vitrification.
  • The biopsy specimen is then sent for Preimplantation Genetic Testing for monogenic disorders. It takes about 10 working days to have the result.