Genetic screening is available through a link with Reprogenetics in Oxford.
Pre-Implantation Genetic Screening (PGS)
Chromosomal abnormality is one of the most common causes of unsuccessful pregnancy. If an embryo has too many or too few chromosomes (a condition called aneuploidy) this can have a serious effect on its chances of developing normally into a fetus and then a baby. In many cases, embryos with the wrong number of chromosomes stop growing by themselves, and this unfortunately often results in miscarriage.
This is no less common with IVF treatment. However, the IVF process enables us to monitor the development of multiple embryos at the same time. We can provide various levels of genetic screening during treatment, to help us select embryos with normal chromosomes, which have the best chance of developing into a healthy pregnancy.
The screenings we offer include array Comparative Genomic Hybridisation (aCGH) and Next Generation Sequencing. Both techniques look at all chromosomes in the embryo, and select those embryos that are chromosomally normal.
How does PGS work?
The first few stages of an IVF cycle that involves PGS are no different from any other, you can see a full IVF journey here.
The difference comes in when the eggs have fertilised in the laboratory. The embryos are frozen on day 1, when they are still one cell, and then transported while frozen in a special shipper to the Reprogenetics lab. There the embryos are cultured to five days (blastocyst stage), and a few cells are microsurgically removed from each embryo, and taken for testing. (Alternatively, a single cell could be removed from each when the embryos are just 3 days in to development – it depends on the development in each case). The cells are analysed to check the chromosomes but the embryos are either returned to the incubator or vitrified or vitrified until the test results are available. If the test results indicate than an embryo transfer will take place, this happens in Oxford.
Scientists working in the laboratory carry out the PGS test on all of the samples received. The test results indicate how many copies there are of each chromosome, revealing any abnormal embryos. PGS does not require additional blood tests prior to the IVF cycle.
Pre-Implantation Genetic Diagnosis (PGD)
Genetic mutations, sometimes passed down from parents, are another cause of unsuccessful pregnancy. Pre-implantation genetic diagnosis is used when a serious genetic disease could be passed from parent to child. There are two techniques: karyotyping, and conventional pre-implantation genetic diagnosis. We are particularly pleased to be able to offer karyomapping as, unlike with conventional PGD, embryos can be screened for chromosomal abnormalities as well as a certain genetic mutation, thus increasing the likelihood of a healthy on-going pregnancy. Conventional PGD is used where the mutation is new and not present in either of the parents, or where we are unable to obtain DNA from other family members who have the same genetic mutation.
Pre-implantation genetic diagnosis can also help couples who have discovered that they have a balanced translocation or inversion. A special high-resolution array Comparative Genomic Hybridisation test can be used to select normal embryos.
How does PGD for a single gene disorder work?
The first few stages of an IVF cycle that involves PGD are no different from any other, you can see a full IVF journey here.
After the eggs are collected, they are fertilised using intracytoplasmic sperm injection (ICSI). The use of ICSI reduces the risk of DNA contamination derived from sperm. Again, the fertilised embryos are transferred to Oxford where they are thawed, and cultured to five days (blastocyst stage).
The cells are analysed for the gene disorder, and the embryos are either returned to the incubator or vitrified (frozen) until the test results are available. Scientists working in the Reprogenetics laboratory carry out the test on all of the samples received and provide the results 24 hours later. Embryos that are unaffected can then be transferred as with the any other IVF journey, and this procedure would take place in Oxford.
Key features of the single-gene PGD service
- By its very nature, pre-implantation diagnosis helps parents avoid having to contemplate pregnancy termination
- It’s available for virtually all single gene disorders*
- These are the most advanced tests anywhere in the world
- Karyomapping is available in most cases, providing ultra-rapid work-up and simultaneous detection of chromosome abnormalities
- Extremely high accuracy rates
If you’d like to discuss the genetic diagnosis options available to you for your IVF cycle, please contact us.
*Disorders must be licensed for testing by the HFEA.
A full list of approved disorders is available at: http://www.hfea.gov.uk/cps/hfea/gen/pgd-screening.htm or contact us for advice.