Pre-implantation genetic testing (PGT)

There are different types of genetic screening for embryos, but they are all ways to check the chromosomes or genes in your embryos for any changes or abnormalities. 

Chromosomes are the structures in your cells that hold your DNA (genetic material) together, and genes are small sections of your DNA that give your body instructions on how to build its components. 

There are three main types of PGT, and they all look for different kinds of genetic changes:

1. PGT-SR checks for structural rearrangements of chromosomes, which are changes in how the chromosomes in an embryo are organised. These changes can affect an embryo’s normal development, leading to pregnancy losses or your baby being born with developmental issues. 
   
   Your consultant may recommend PGT-SR if you or your partner have been diagnosed with abnormal chromosomes that might have caused you difficulties conceiving or repeated pregnancy losses. PGT-SR aims to give you the best chance of a successful pregnancy by identifying embryos with normal or ‘balanced’ chromosomes for implantation.
   
   
2. PGT-M checks for monogenic defects, which are changes to single genes. These changes can cause genetic diseases such as cystic fibrosis or Huntington’s disease. If you have a family history of any genetic diseases, PGT-M can help determine the chances of those diseases being passed on to your child. 
   
   
3. PGT-A checks whether your embryos have the right number of chromosomes they need. The test is looking for a condition called aneuploidy, which is a change in the number of chromosomes in your embryo. Having the wrong number of chromosomes might mean that your embryo doesn’t develop into a baby or might cause conditions such as Down’s syndrome and Turner syndrome.  
   
   PGT-A isn’t looking for any specific conditions that you or your partner might pass on, or for any inherited conditions. It’s a screening test to check for a wide range of genetic problems that can develop in any embryo.

1. You’ll have hormone injections that stimulate your ovaries, so they produce eggs. Then your eggs need to be collected, so you’ll be mildly sedated and have a vaginal ultrasound, before a thin needle collects them through your vaginal wall.
2. Then your eggs will be fertilised with sperm in a laboratory, so they can produce embryos. This is either done using IVF or Intracytoplasmic Sperm Injection (ICSI), depending on what you and your consultant have decided is best.
3. Your embryos develop for up to six days until they reach what’s called the blastocyst stage. When they’re ready, we’ll carry out an embryo biopsy, which means we’ll remove some cells from each embryo. We only take cells that will form the placenta, and it’s a safe procedure with a low risk of harming your embryos.
4. Then we can test those cells to see if they have any potential genetic issues that could affect your pregnancy. We’ll freeze your embryos to pause their development while we wait for the results of the tests.
5. Once we know the results, we can find your most viable embryos to transfer to your womb. We might find several, but we usually only transfer one at a time. You can freeze and store any ‘extra’ viable embryos in case you want to use them in the future.