(+34) 951 087 975
Preimplantation genetic testing (PGT) is a highly useful tool in assisted reproduction, which is designed to test if embryos, resulting from an in vitro fertilization process, are genetically normal, before they are transferred to the uterus. The aim is to increase the probability of the embryo implanting into the uterus and giving rise to a successful pregnancy and the birth of a healthy baby.
This useful technique is often employed when the intended mother is of an advancing maternal age, as the DNA within the egg cells gets damaged over the years, if previous implantation failure has been experienced, or when there is a need to check for any genetic alterations due to possible hereditary diseases. It can also be used for family balancing, as the sex of the embryo will be known.
In this article we take a look at PGT, and whether it is recommended and /or useful when used in combination with egg donation treatments.
WHAT IS PREIMPLANTATION GENETIC TESTING?
To answer this question, we will look at the two types of PGT that are used in assisted reproduction treatments these days.
PGT-A: Aneuploidy
PGT-A is a test performed on embryos created via IVF. It is a genetic test to look for chromosomal abnormalities, such as the presence of extra chromosomes, bits of chromosomes and missing chromosomes. When an embryo has the incorrect number of chromosomes it is known as aneuploidy. In IVF treatments, PGT A screens for genetically normal, euploid embryos as these have a better chance of implanting correctly into the uterus and giving rise to the desired pregnancy.
Since PGT-A identifies the individual chromosomes, it will also show which X or Y chromosomes are present, and so can be used for family balancing, if your country allows you to know the gender of the embryo and make transfer choices based upon it.
PGT-M: Testing for mutations
PGT-M is used to screen for specific mutations in the embryo DNA. It is particularly useful if there is a history of genetic conditions in your family or your partner has a autosomal dominant condition, it will detect if an embryo carries the undesirable genetic mutation. It can be carried out when requested to give extra reassurance for the safety of the child.
HOW AND WHEN IS PGT PERFORMED
To carry out PGT, a sample of the embryo’s genetic material must be obtained. This is done by performing an embryo biopsy, where a blastocyst is carefully manipulated by an embryologist to remove one of the outer cells (from the outer layer, called the trophectoderm), without harming the blastocyst, so that the DNA can be analyzed. Although it is an invasive procedure, the embryos are usually unharmed.
Embryo biopsy for preimplantation genetic testing
The blastocyst(s) is then vitrified (frozen) while the awaiting the results of the testing. Any genetically normal embryos can be thawed and used in an embryo transfer at a later date.
SHOULD I PGT TEST MY EMBRYOS WHEN I AM USING DONOR EGGS?
When using donor eggs for an IVF treatment, the eggs will be from a young healthy donor. As the donor is young, and thoroughly screened for health, the eggs will be of a very high quality, and you would expect the embryos formed after fertilization to be genetically healthy.
Indeed, in a study on women using their own eggs for IVF, published in the journal “Fertility and Sterility” in 2013*, it was demonstrated that the number of genetically normal embryos, termed euploid embryos (meaning containing the correct number of chromosomes produced from IVF treatments) decreases with the maternal age. In summary, the younger the woman, the more normal embryos and therefore less requirement for PGT-A testing. As donor eggs are from young women, we can expect the majority of embryos formed from them to be genetically normal.
If we take a look at another very interesting and highly relevant study published in 2020 in the scientific journal “Human Reproduction”, they concluded that there was no increase in successful pregnancy outcomes when the recipients of donor eggs tested the resulting embryos for aneuploidy (PGT-A) **.
Taking these results together we can say that at present, there is no evidence that PGT-A testing on embryos obtained from donor egg IVF leads to increased success rates, when the eggs come from a young, healthy donor such as Ovobank. However, it is always an option which is open to you if you wish, and personal choice must always be taken into consideration to personalize treatments.
If you are concerned about the embryos containing any genes that would lead to genetic diseases, you can opt for PGT-M testing, whatever the age of the egg donor.
If you have any questions, or would like to chat to one of our coordinators about using frozen donor eggs, then you can get in touch with us in any of the following ways:
EUROPE: +44 2037691300
NORTH AMERICA: (213) 221-0080
