Pre-implantation Genetic Testing for Carriers of Chromosome Rearrangements (PGT-SR)

Description: Pre-implantation genetic testing (PGT) for chromosome rearrangements is carried out by SNP array. This test can be offered to couples requiring tests for the following: 1. Reciprocal translocations 2. Robertsonian translocations 3. Inversions and insertions 4. Deletions and duplications 5. Complex chromosome rearrangements (CCRs) 6. Sexing for an X-linked condition The material used for testing is material obtained from the trophoblast from blastocyst stage embryos (trophectoderm biopsy). The biopsy is taken on day 5, 6 or 7 post-fertilisation.

Clinical details

Pre-implantation genetic testing (PGT) is available to couples that are at risk of having a child with an unbalanced chromosome rearrangement; it can also be used for sexing for a familial X-linked condition (if a mutation is not known).

IVF protocols are used to obtain and fertilise a number of eggs. The fertilised embryos develop for five to seven days and then the trophectoderm layer of each embryo is biopsied to collect approximately ~5-10 cells. The genetic material (DNA) from the cells is tested for the known chromosome rearrangement in the family. Unaffected embryos are then transferred into the uterus, with the aim of establishing a pregnancy unaffected by imbalance for the chromosomes tested or the specified X-linked condition.

The genetics laboratory works closely with the Centre for Pre-implantation Genetic Testing at Guy’s and St Thomas’ Trust which is the largest and most successful centre in the UK for PGD for chromosome rearrangements and monogenic disorders, with over 700 babies born as a result of this treatment.