Preimplantation Genetic Diagnosis (PGD) Overview
Preimplantation genetic diagnosis (PGD) is a procedure that might be recommended to reduce the risk of passing genetic and chromosomal abnormalities on to your children.
With PGD, specialists look for genetic defects within your embryo during the in vitro fertilization (IVF) process. Using sophisticated tests, doctors can determine if the embryo is a carrier of genetic disorders or diseases before implantation.
Depending on the DNA results, you and your partner can decide if the pregnancy should continue.
The link between PGD and IVF
Preimplantation genetic diagnosis is done during the in vitro fertilization process. IVF consists of the following steps:
- Egg Monitoring and Retrieval
- Semen Donation and Fertilization
- Embryo Transfer
Preimplantation genetic diagnosis is done after a sperm fertilizes an egg, yet before the fertilized embryo is transferred to your uterus.
Identifying healthy embryos
The preimplantation genetic diagnosis process involves the following steps:
- After an embryo has divided into eight cells, one cell is removed.
- DNA is extracted from this cell. This material in the cell is what’s passed on from the parents to the child.
- Through various procedures, the DNA is evaluated to see if there are any identifiable health problems.
- If the embryo is found to be healthy and free of genetic disorders, then the IVF cycle may continue and the embryo will be transferred into your uterus.
- If a genetic disorder is identified, you and your partner may then choose whether you want to continue and use that embryo to get pregnant.
Who’s a candidate for PGD?
If you and your partner have been tested and are at high risk for passing on genetic disorders, you may be a good candidate for preimplantation genetic diagnosis. Currently, PGD is used to test for the following genetic and chromosomal disorders:
- Single gene disorders (caused by a mutation in one gene)
- Recessive and dominant sex-linked disorders (caused by genes carried on the sex chromosomes)
- Chromosomal rearrangements and alterations
The following groups of people may be best suited for PGD:
- Women who become pregnant after age 35, as the risk of having babies with chromosomal abnormalities is higher
- Couples at high risk of having children with genetic and chromosomal disorders who want to increase their risk of having a healthy child
- Women who have had recurrent miscarriages or pregnancy losses that are linked to chromosomal problems with the fetus
Couples who use PGD must undergo the IVF procedure, whether they are infertile or not. In addition, counseling is required for any couple that chooses to use preimplantation genetic diagnosis.
Does PGD affect pregnancy rates during IVF?
If you are considering PGD and IVF, you may be concerned about the risk of not being able to use all of your fertilized embryos. Some experts say that PGD will not affect the success rates of IVF. However, if an embryo is found to have genetic or chromosomal abnormalities, it might not be implanted into the uterus. This would reduce the number of embryos that can be transferred.
In addition, PGD can be very expensive, and some insurance companies may not cover the cost, which may make couples less likely to continue with IVF.
Not a perfect process
Sometimes doctors will identify an embryo or fetus to be at risk for a genetic disorder, but the baby may grow up without ever showing signs of the disease or abnormality.
Embryos that do have problems are sometimes misdiagnosed as healthy, and then transferred to the female. A baby could then be born with unexpected problems.
In addition, doctors can mistakenly identify a healthy embryo as abnormal, causing a perfectly healthy embryo to be discarded.
Experts recommend that if a couple’s embryos show no genetic or chromosomal abnormalities during PGD, and the woman gets pregnant, more testing should be done during the pregnancy to make sure the baby is healthy.Sources
- American Society for Reproductive Medicine. Preimplantation genetic testing: a Practice Committee opinion.
- American Pregnancy Association.
- PGD Tuberous Sclerosis Alliance. PGD Journal of Histochemistry and Cytochemistry. PGD: An Overview