These are diseases that occur due to abnormalities at chromosomal level, passed down to the offspring by the parents.
What is preimplantation genetic testing?
This refers to the two types of tests performed on embryos during IVF, preimplantation genetic screening (PGS) and preimplantation genetic diagnosis (PGD).
Fertility specialists conduct these tests to determine if embryos have genetic abnormalities which often cause failed implantation and miscarriage, leading to unsuccessful IVF. Embryos with such defects are excluded from being transferred to the uterus.
This testing increases the likelihood of becoming pregnant, also improving live birth rates using IVF.
Benefits of preimplantation genetic testing:
- Lower risk of a genetic disorder in the child.
- Higher possibility of a healthy pregnancy and successful birth by IVF.
Preimplantation Genetic Diagnosis (PGD) is a reproductive technology used along with IVF to increase the chances of a successful pregnancy and delivery. This test is suitable for patients with a family history of single gene disorder. PGD is a genetic test on cells removed from embryos to help select the best embryo(s) to achieve pregnancy or to avoid a genetic disease for which the couple is at risk.
Single gene the test picks up includes:
- Cystic Fibrosis
- Fragile X
- Huntingtons’ disease
- Spinal Muscular Atrophy.
- Duchenne muscular dystrophy
- BRCA1/BRCA2 (hereditary breast/ovarian cancer)
Who should consider PGD?
PGD may be considered in all IVF cycles. Those who might benefit the most from it are couples at increased risk for chromosomal abnormalities or specific genetic disorders. This comprises of women who have had numerous miscarriages, or who have had a previous pregnancy with a chromosome deformity. Women past 38 years of age and men with some types of sperm abnormalities may produce embryos with higher rates of chromosome abnormalities.
How is it done?
Once the embryos are created in the lab, they are grown for five to six days. On fifth or sixth day, the biopsy for PGD is done on all appropriately developed embryos. Biopsy involves removing a few cells from the embryo. The genetic material inside the cells is tested for abnormalities. Based on this test, the healthy embryos are then transferred to the uterus for implantation.
What is genetic testing in IVF?
In IVF, genetic screening of embryos is called pre-implantation genetic screening (PGS).
Why do we test embryos?
PGS is done to check that the developing embryo has the right number of chromosomes before implantation. This is done on 5/6 day of development of the embryo.
PGS can be particularly useful for:
- Recurrent miscarriages
- Women over 35
- Family history of chromosomal disorders
- Previous unsuccessful IVF cycles.
This screening test helps us pick healthy embryos for implantation, reducing the number of treatment cycles.
Types of testing
Embryo or blastomere biopsy
Embryo biopsy is the most technique used. A few embryonic cells are removed on day 5 of development.
How are the cells analysed?
EmbryoScreen is based on NGS technology, one of the fastest and most accurate technology available.
Embryonic cells biopsied go through Whole Genome Amplification to millions of their copies. DNA is then fragmented and analysed against the human genome.
This test can identify abnormal conditions like extra chromosomes (trisomy) or a missing chromosome (monosomy).