Preimplantation Genetic Screening (PGS)/Preimplantation Genetic Diagnosis (PGD)

Preimplantation Genetic Screening (PGS)

Recommended for:

  • Advanced age females, 38 years old and above
  • Those who have miscarried more than two times
  • Repeated failure with assisted reproduction
  • There is a family history of chromosomal abnormalities or chromosomal translocations
  • Those who want to avoid fetal chromosomal abnormalities

Preimplantation Genetic Screening: refers to chromosomal examination before implantation. This genetic screening can detect abnormalities in all 23 pairs of chromosomes, large fragment deletions.

Limitations of this procedure:

The primary examination of PGS is the normalcy of chromosome number and 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 PGS.

 

Approach to PGS:

  • 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 the day 14 of the menstrual cycle and a consent is signed for PGS 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 Screening (PGS) / Next Generation Sequencing (NGS) , it will take about 10 days to have result.

 

Preimplantation Genetic Diagnosis (PGD)

Preimplantation genetic diagnosis 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, 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 free of the genetic disease are chosen for transfer to the prospective mother’s uterus.

Limitations of this procedure:

The aim of PGD 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 PGD.

Approach to PGD:

  • Start enquiry at our infertility clinic for proper consultation and assessment.
  • Patients will provide the family genetic history checklist or a pedigree table 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 PGD and to pay the fee for the probe design.
  • After completion of the probe, patient 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 remove from the outer layer of embryothis calls a trophectoderm biopsy). The embryos are frozen immediately using vitrification.
  • The biopsy specimen is then sent for Preimplantation Genetic Diagnosis, it will take about 10 working days to have result.