What Is Genetic Testing?
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The Process
With the process of In Vitro Fertilization (IVF), we can fertilize the egg with sperm and produce embryos. The embryos are cultured in a laboratory for 5-6 days as they develop into the blastocyst stage, after which an embryo biopsy is performed.
The embryologist performs an embryo biopsy using a laser under the control of an inverted microscope. At AFCT, the embryo biopsy is performed personally by Dr. Dmitri Dozortsev, a President of the American College of Embryology who was one of the pioneers and the developer of the embryo biopsy techniques at the Reproductive Genetics Institute in Chicago.
Dr. Dozortsev continues to innovate by creating new tools improving embryo biopsy, such as ENVETM holder and VitroholderTM (www.invitrolife.com).
Recently Dr. Dozortsev developed a new method for embryo biopsy, Minimal Impact BiopsyTM , which increases safety of the embryo during the procedure.
http://ivfconundrums.com/reproductive-laboratory/minimal-impact-biopsy-human-embryo-mib-dr-dmitri-dozortsev
He prepares a set of custom-made microtools for each embryo biopsy to maximize its safety and effectiveness.
The biopsy material is sent for testing by a courier, while embryos are frozen awaiting for the results from the test.
Studies have shown that close to 50% of embryos, even from the best patients, can be abnormal. The proportion of abnormal embryos increases with woman’s age (usually after the age of 35, with a more dramatic increase in abnormality after the age of 40).
The vast majority of chromosomal errors are called de novo random errors, meaning the patient has no predisposition to any particular type of error or family genetic transmission. The visual appearance of chromosomally abnormal embryos will appear completely normal to an embryologist but will fail to implant, end up in a miscarriage, or develop a child with chromosomal abnormalities.
The Role of Genetic Counseling in IVF
For couples seeking IVF treatment, genetic counseling could be a crucial first step.
Every year, millions of couples struggling to conceive turn to In Vitro Fertilization (IVF). According to the Centers for Disease Control and Prevention, approximately 1.7% of babies born in the US each year are conceived with the support of Assisted Reproductive Technology (ART).
If you’re coping with infertility or recurrent miscarriages and considering IVF, genetic counseling may be an important first step
The Role of Genetic Counseling
Genetic counseling serves two functions:
A) To help identify if a genetic condition is at the root of your infertility
B) Increase your chances of successful implantation through IVF.
What causes infertility and persistent miscarriages varies depending on the couple. While in many cases it’s a result of hormonal or anatomical factors, some couples do experience difficulty conceiving for genetic reasons. For both men and women, this can be in the form of a chromosome translocation, an abnormality in which chromosomes swap material. Balanced translocations are responsible for up to 5% of couples facing recurrent miscarriages.
Other genetic factors for men include Klinefelter syndrome and Y chromosome deletions, two conditions that can limit sperm production. Women may be at risk for genetic ovulatory disorders, including Kallmann syndrome and fragile X syndrome. Genetic screening can identify if a chromosomal abnormality is behind your difficulties conceiving and help you better understand your treatment options.
Chromosomal abnormalities are also a primary cause of failed IVF attempts. This has led many couples to undergo preimplantation genetic testing. Preimplantation genetic testing can determine which embryos carry genetic abnormalities, thereby giving couples the option to remove those embryos from the sample and increase their chances of successful implantation. Men and women who have a history of life-altering genetic disorders, including muscular dystrophy, cystic fibrosis, and breast and ovarian cancer, may also choose to use preimplantation genetic testing to select embryos with a lower risk. The vast majority of chromosomal errors are called de novo random errors, meaning the patient has no predisposition to any particular type of error or family genetic transmission. The visual appearance of chromosomally abnormal embryos will appear completely normal to an embryologist but will fail to implant, end up in a miscarriage, or develop a child with chromosomal abnormalities.
Types of Preimplantation Genetic Tests
There are two forms of preimplantation genetic tests — preimplantation genetic screening (PGS) and preimplantation genetic diagnosis (PGD). Both PGS and PGD can help increase the chances of a successful birth through IVF and lower the risk of passing on a genetic disorder.
PGS differs from PGD in that it examines each embryo to determine the number of
chromosomes it contains. A healthy embryo should have 46 chromosomes — 23 from each parent. An embryo that is missing a chromosome or has an extra one is called an aneuploidy.
An aneuploidy is more likely to result in failed implantation, miscarriage, or genetic defects, including Down syndrome, Turner syndrome, and Patau syndrome. A couple considering IVF should see a genetic counselor for PGS if they:
- Had an aneuploidy pregnancy in the past
- Experienced at least two miscarriages
- Hadr previous trouble with implantation
- Have been diagnosed with infertility
- Are over 35 years old
Some couples may choose PGD in addition to or independently from PGS. PGD inspects embryos for genetic mutations that either one or both of the parents believe they carry.
These mutations can appear in the form of several genetic disorders, including Huntington’s disease, sickle cell anemia, muscular dystrophy, cystic fibrosis, fragile X syndrome, Tay-Sachs disease, and hereditary forms of breast and ovarian cancer. Couples with a family history of single-gene disorders such as these and those who have experienced repeated IVF failures or recurrent miscarriages should discuss PGD with a genetic counselor.
