PGD can offer some couples a peace of mind, others, a glimpse of uncertainty. What to expect and how to become informed before making your decision.
PGD – Preimplantation Genetic Diagnosis – is an advanced and cutting-edge technique that is becoming more and more common within In Vitro Fertilization (IVF) treatments. It is a procedure used prior to implantation by embryologists to detect various factors in the viability of the embryos. PGD prevents the transmission of serious diseases caused by genetic and chromosomal alterations in embryos to offspring and is also able to determine the gender of your unborn child, all before embryos are transferred to the uterus.
This early detection of chromosomal abnormalities classified as “numerical” (aneuploidy) – abnormal numbers of chromosomes – or “structural” (deletions, duplications, translocations or inversions) – alterations in a chromosome’s structure -, also helps to reduce the probability of suffering a miscarriage and increases the chance of a healthy offspring. Given the standard definition of what PGD is capable of, it seems like a simple choice to make. However, as with every medical procedure, there are still both pros and cons to be considered.
How Does PGD Work
PGD is usually performed in the earliest stages of embryo development (Day 3 or Day 5-6), prior to transfer into the womb. In an IVF cycle, gametes (oocytes and/or sperm) are collected from intended parents or donors and then fertilized in a lab settling (Day 0). One day later (Day 1), the embryologist will check how many embryos have begun to develop as a result of the fertilization process. After about three days (Day 3), the embryos have between 6-10 cells. After this they’re placed in a specially adapted environment called “co-culture” to keep growing. These embryos continue to develop until they reach the blastocyst stage (Day 5-6), which means that they stay in the lab slightly longer.
During the PGD process, a fragment of the trophectoderm (a layer of cells on the outer edge of a blastocyst) is removed from the embryo via a biopsy without compromising its development. Removal of this fragment has no adverse side effects on the future embryo development. It will keep growing and producing cells.
The genetic analysis is carried out on several cells of this fragment. This allows the chromosomal and genetical structure to select healthy embryos. If abnormalities are found, the embryo won’t be selected for implantation.
Benefits of PGD
PGD has a range of proven medical benefits for both mother and child. One of them is an accurate and improved embryo selection. After this analysis, only the healthiest and most suitable embryos will be selected for implantation. Those with abnormal results won’t be used for a transfer.
PGD informs embryologists how the embryo is developing and what its chromosomal map looks like. Our genetic information is a blueprint that designates the functionality of living cells. Abnormalities found in the genetic code through the PGD suggest birth defects or disease patterns that may severely limit the viability of the embryo or the health of the baby.
Generally, embryos that have been analyzed through the PGD reduce the probability of miscarriage. This is because PGD detects chromosomal abnormalities which can cause a miscarriage before implantation. In natural conception, many embryos that present congenital defects are eliminated by natural means. This technique has high success rates when identifying genetic and chromosomal abnormalities. This increases significantly with age as egg quality and viability decreases as women age.
PGD allows single embryo transfers which means multiple pregnancies are reduced. In the past, it was normal for women to be implanted with multiple embryos during IVF, in case some of them were not viable. Despite this, some women would not get pregnant at all, but others would experience twins, triplets, or even higher numbers. A multiple pregnancy is a serious scenario. The expectant mother is exposed to a greater risk of complication which can jeopardize the health for both mother and babies. Fortunately, the early detection of the embryo’s viability enables single embryo transfer at blastocyst stage and a higher success rate of pregnancy.
Disadvantages of PGD
Medical tests help us to make better and more informed decisions. But we must remember that most tests are not 100 per cent reliable. Because of this, many practitioners still advise parents to perform prenatal genetic testing as well. These tests increase the cost associated with IVF treatments. PGD treatments are usually not covered by medical insurance plans. Which means, they are not always a viable choice for all couples.
Some couples also experience a moral and emotional conflict when making the decision to perform PGD. Embryos with chromosomal defects are considered unsuitable and then discarded, which can be a very uncomfortable reality. It can also be a difficult situation for couples who are unable to provide a great number of embryos, to begin with. Those embryos are developed past the standard three days so that they can reach the blastocyst stage. This means they may be eligible for biopsy.
The Choice is Yours
Ultimately, there are many benefits that are associated with PGD, as well as a few risks. The decision to move forward with PGD must be considered by all couples. Infertility comes with many difficult questions and it’s important to discuss these doubts and concerns with your family and your physician/medical team. The right choice will always be what’s best for you and your future family.