PGT for aneuploidy screening

What is PGT-A?

Preimplantation Genetic Testing for aneuploidy (PGT-A) is a genetic screening that can be performed on the embryos during an IVF treatment, before they are implanted in the womb. It allows detecting abnormalities in the number of chromosomes (aneuploidies) and transferring only the embryos that are chromosomally normal (euploid).

Humans have 46 chromosomes in each cell of their body. Although most embryos cannot survive with a missing (monosomy) or extra (trisomy) chromosome/s and are related to implantation failure or spontaneous miscarriage, some others can survive till birth leading to a baby affected of a genetic syndrome (for example, trisomy 21 related to Down Syndrome). Thus, by screening the embryos for chromosomal aneuploidies we can help couples to:


  • Increase pregnancy rate
  • Decrease miscarriage rate
  • Reduce the risk of a baby with a chromosomal syndrome

Different options of chromosomal screening are available: 24-chromosomes, 9-chromosomes (X, Y, 13, 15, 16, 17, 18, 21, 22), 5-chromosomes (X, Y, 13, 21, 18)  or 3-chromosomes (X, Y, 21) test.

How is it performed?

  1. In Vitro Fertilization cycle to obtain embryos performed in an Assisted Reproduction unit.
  2. Embryo Biopsy: can be performed on day 3 or Day 5 of embryo development and consists of removing one cell (day 3) or small groups of cells (day 5) from the embryo without compromising its normal development.
  3. Genetic Testing: the cell or cells obtained from the embryo are processed for genetic analysis by PGDlabs team. The test, which can be performed by FISH or NGS technologies, allows us to determine those embryos that have a normal number of chromosomes.
  4. Embryo Transfer: The results of the genetic test are transmitted to the assisted reproduction unit and the embryos that are most likely chromosomally normal are transferred.

Who can benefit?

Chromosomal abnormalities occurred naturally during egg and/or sperm formation or in the first steps of embryo development and can involve any chromosome. However, some specific groups of patients are at higher risk to develop chromosomally abnormal embryos and can preferentially benefit from PGT-A:

  • Infertile couples with two or more IVF cycles without pregnancy
  • Couples with repeated miscarriages (with 2 or more previous miscarriages)
  • Women with advance maternal age (over 36 years old)
  • Men with abnormal result in sperm FISH
  • Couples with a previous affected pregnancy or baby of a chromosomal syndrome