Preimplantation Genetic Diagnosis (PGD)
NEW!! GIVF Offers PGD Testing for Chromosome Abnormalities by Next Generation Sequencing (NGS)
Since January 2018 the PGD Laboratory at Genetics & IVF Institute has been offering PGD testing for aneuploidy and structural chromosome rearrangements by Next Generation Sequencing DNA analysis. We use the Illumina®
platform with VeriSeq and BlueFuse data analysis software.
24 Chromosome Testing is a genetic test on embryos to screen for common and uncommon chromosome abnormalities as well as the X and Y chromosomes. This test can identify if an embryo has extra or missing chromosomes, (aneuploidy). Only embryos with the correct number of chromosomes are selected for transfer into the woman’s uterus. This analysis also goes by the name PGT-A (aneuploidy testing).
It is known that one of the major causes (60-70%) of failed implantation and early miscarriage is extra or missing chromosomes in the embryo. The exact percentage of chromosomally abnormal embryos that each couple produces is related to many factors including maternal age, number of failed IVF cycles, and the type and quality of sperm used. By selecting the best embryos for transfer, this testing may decrease the miscarriage rate and increase the implantation rate.
What makes 24 Chromosome NGS Testing different from previous aneuploidy screening options?
- Next Generation Sequencing is currently the most sensitive and comprehensive chromosome analysis available. We use the Illumina®platform with VeriSeq and BlueFuse data analysis software.
- 24 Chromosome NGS Sequencing evaluates all 24 chromosomes (all 22 non-sex chromosomes and the X and Y chromosomes) for numerical abnormalities prior to transfer.
- The NGS method of testing is more comprehensive and sensitive than past methods and allows for the identification of high quality embryos for transfer.
- Embryos tested with 24 Chromosome NGS Testing that are determined to be normal are felt to have a much higher chance to result in a successful pregnancy.
24 Chromosome NGS Testing may be of particular use to patients who have:
- A history of multiple pregnancy loss
- Unsuccessful IVF attempts despite transfer of good quality embryos
- Severe male factor infertility
- A prior pregnancy with chromosome abnormality, or
- If the man or woman is a carrier of a chromosome rearrangement, such as a translocation.
24 Chromosome Microarray is also an option for any woman who wishes to reduce her chances for chromosome abnormalities associated with the age of her eggs.
PGD for Gender Information
For couples requesting to know the gender of their embryos, PGD for aneuploidy by Next Generation Sequencing can provide information regarding the sex chromosomes. This test screens embryos for abnormalities of chromosomes numbers 1-22, and the sex chromosomes X and Y. Since gender is determined by the number of X and Y chromosomes present in each embryo, this test identifies which embryos are male or female in addition to the status of the 22 non-sex chromosomes. Patients may choose to use only embryos of the desired gender to attempt a pregnancy. Decisions about which embryo(s) to transfer and disposition of any remaining embryos are made with the consultation of the medical and genetics team. Patients interested in knowing gender information on their embryos should discuss this request at the initial physician consultation.
PGD for Genetic Disease
A PGD test can be designed for almost any genetic disease as long as prior testing on the individual has identified the genetic/molecular cause of their condition.
Who benefits from PGD for Genetic Disease?
A person who has an autosomal dominant genetic condition has a 50% chance of having a pregnancy with the same condition. Prenatal diagnosis by amniocentesis or chorionic villus sampling often allows diagnosis of the genetic disease during pregnancy. However, many couples do not want to be faced with making a decision regarding the outcome of their pregnancy. PGD is an alternative testing option that allows embryos to be tested for the disease prior to implantation in the uterus.
Similarly, couples who each carry a mutation for the same autosomal recessive genetic condition have a 25% chance to have a pregnancy affected with this genetic disease. While prenatal diagnosis by amniocentesis or chorionic villus sampling often allows diagnosis of the genetic disease during pregnancy, couples may wish to consider PGD for the specific disease so that only embryos without the disease are used for pregnancy. Whether or not to transfer embryos that are carriers of an autosomal recessive disease is a personal choice and the genetics team would discuss this option individually with each patient.
When a couple is at risk to have a child affected with an X-linked disease, couples can elect PGD for 24 Chromosomes for the purposes of identifying embryos of a specific gender. If prior testing has identified the genetic cause of the disease, custom PGD for the specific genetic disease would also be an option.
What makes this test unique?
PGD for a specific genetic disease is a specialized test that has to be adapted to work on a small amount of DNA from biopsied embryos. The tests are developed individually for each family based on their history, prior testing results, and family studies. Prior to the initial IVF cycle, the PGD Laboratory would need a blood sample from the couple themselves and may request blood or buccal (cheek) swab collection from one or more family members as well. Once the test has been designed and optimized for that couple, the PGD laboratory will be able to run the analysis on embryos from one or more than one IVF cycle, as needed. One of the genetic counselors at Genetics & IVF will guide the patient in acquiring the necessary samples and is available to answer any questions along the way.
The test is designed to identify the presence or absence of the specific gene mutation(s) that cause the disease in that family. In addition, linked markers (or unique DNA identifiers near the mutation(s)) are identified in the family studies ahead of time. Embryos are also tested for the markers, and it is this combination of both a mutation test as well as linked markers that results in a robust PGD test with high accuracy. It is this combination of both mutation testing and markers that also separates the PGD Laboratory at Genetics & IVF Institute from other laboratories offering PGD.
Will my embryos be tested for anything else besides the one specific disease?
Yes. In addition to the known genetic disease, biopsied embryos will also be tested for 24 Chromosomes by NGS to screen for common aneuploidy. Only embryos unaffected for the genetic disease and with a normal chromosome result would be considered available for transfer. Whether to use or not use embryos that are carriers of an autosomal recessive or X-linked disease will be discussed individually with each patient. The combination of PGD for genetic disease as well as aneuploidy screening by 24 Chromosome Microarray will help identify the best embryo(s) to use with the greatest chance for a healthy outcome.
Non-disclosing PGD for Huntington disease is available.
Huntington disease (HD) is an adult onset disorder involving progressive motor disability, cognitive decline, and personality changes. Because this is an autosomal dominant condition, a person with a parent with HD has a 50% risk of developing HD. Many couples want to prevent having a child who will develop HD, but do not want to face the decision of prenatal testing or making a decision about their pregnancy. Often, individuals do not know if they have HD when they are family planning because the average age of onset of clinical symptoms is approximately 40 years old. These couples may want to prevent having a child with HD, but also do not want to know if they carry the HD gene. Non-Disclosing PGD for HD can help these couples decrease the chance of conceiving a pregnancy with HD while not identifying the HD status of the couple. PGD for HD is also available when couples already know their HD status and wish to prevent transmission to the next generation.
Genetics & IVF Institute was a pioneer in non-disclosing PGD (now PGT) for Huntington’s Disease, which still benefits parents, today, as noted in this article highlighting a grateful mother and past GIVF patient.
PGD for BRCA and other cancer predisposition genes is available.
When there is a personal or family history of cancer, genetic testing may have been performed to identify the underlying genetic cause. This guides cancer surveillance recommendations and management of the cancer. It also helps identify other family members who may also be at-risk. Some couples wish to prevent having a child with the same gene and the associated cancer risks. PGD for the specific cancer gene can be designed and performed in the exact same way that custom PGD for other genetic diseases is completed. Genetics & IVF also specializes in oocyte preservation for cancer patients. Women with cancer diagnoses are encouraged to consider cryopreserving (freezing) unfertilized oocytes prior to initiating cancer treatments that may negatively affect their future fertility.
I am interested in PGD for Genetic Disease. How do I get started?
The Genetics & IVF staff is ready to work with you to have a healthy pregnancy. Prior to making an initial appointment, please ask to speak with one of the genetic counselors at Genetics & IVF to briefly discuss your history and reason for considering PGD. The genetic counselor will assist with your initial steps, which include a consultation with one of the directors of our PGD program. The purpose of this consultation is not to repeat information about the disease or its inheritance already familiar to the patient, but to discuss the unique details of how PGD is performed. This includes timing, accuracy, and methodology, as well as provides an introduction to the IVF and PGD processes. A copy of the prior testing results identifying the cause of the genetic disease is requested ahead of time for review.
Schedule an appointment, or call 800.552.4363 or 703.698.7355.