Embryo screening PGD, PGS and PGT

Embryo screening involves testing embryos during IVF to assess for chromosome abnormalities before embryo transfer. IVF cycles can fail for many reasons but in some circumstances, this can be due to chromosome abnormalities.

Why choose Embryo Screening?

DNA is divided into pairs of chromosomes, one each inherited from the egg and sperm cell. An abnormal number of chromosomes (known as aneuploidy) occurs by gaining an extra chromosome or losing one and can occur in embryos following IVF. Chromosome abnormalities mean that the embryos may implant or develop into a healthy pregnancy and live birth. In some cases, however, pregnancies can occur but later miscarry or, in a small minority, result in abnormal pregnancy and live births. It is estimated that at least 50% of miscarriage are caused by aneuploidy in both natural and IVF pregnancies.

Who would benefit from Embryo Screening?

Preimplantation Genetic Diagnosis (PGD) is a screening test that has been used since the 1980’s and has now been developed to include not only testing for known genetic conditions, that one or both parents may have or be carriers for, but also PGD can be an option for older women or couples who have had previously unsuccessful IVF, recurrent miscarriages or severe male factor infertility.

To add to the fertility terminology and acronym confusion, these tests have been called Preimplantation Genetic Testing for Aneuploidy (PGT-A) and Preimplantation genetic testing for monogenetic diseases (PGT-M).

Embryo Screening for IVF

Embryo screening using Preimplantation Genetic Testing for Aneuploidy (PGT-A) can help identify genetically unbalanced embryos. Women in their late thirties and early forties are at a significantly increased risk of chromosome abnormalities and are therefore more likely to have a higher incidence of genetically unbalanced embryos following IVF. PGT-A is also able to identify genetic abnormalities that may have resulted in failed implantation.

Embryo Screening for known genetic conditions

One child in every 100 babies are born an inherited genetic condition that can often have a devastating impact on the whole family.  Preimplantation genetic testing for monogenetic diseases (PGT-M) such as Cystic Fibrosis, Thalassaemia, Huntingdon’s disease and Sickle Cell Anaemia is an option for couples wishing to avoid the risk of having a child with a genetic disease.

PGD and PGS Benefits

PGD and PGS offer several benefits to those who choose to include it in their IVF cycle. First and foremost, both can reduce the risk of passing on genetic abnormalities to babies conceived with IVF. Couples going through IVF often have to go to great lengths just to become pregnant. Losing a pregnancy due to an inherited abnormality could be devastating. While PGD and PGS are not 100% guaranteed, they do reduce the risk.

Side Effects and Risks

Screening embryos for abnormalities do come with some risk, which is essentially the potential for embryos to be damaged in the process. When a portion of the embryo is removed for testing the rest of the embryo has to stay intact. Otherwise, implantation could fail or the embryo might not survive.

Embryologists carefully perform the procedure so that risks to the embryo are minimal. However, it is important to ask your clinic about their success rate and exactly what process they adopt.

Couples and women considering this testing should understand the cost and the implications. The cost of PGD/PGS adds significantly to your cost of IVF, however, in some circumstances, you may be able to obtain the testing on the NHS if you live in the UK. The test is controversial and not included in the NICE Guidelines for fertility. It is therefore important to discuss this procedure with your clinic to fully understand the risks and implications before going ahead with the treatment.