Prenatal Genetic Diagnosis for Angelman Syndrome
If you have a family history of Angelman syndrome and are expecting, you may want to consider prenatal genetic diagnosis.
What is prenatal genetic diagnosis?
Prenatal genetic diagnosis means determining, before birth, whether your baby has a genetic disease such as Angelman syndrome.
During pregnancy, you meet frequently meet with your prenatal physician to ensure your and your baby’s health. Your doctor checks your baby’s weight, size, and development at every appointment. However, for diseases like Angelman syndrome, a genetic test may be necessary to diagnose your baby before birth.
Amniocentesis involves taking a sample of the amniotic fluid, which is the liquid surrounding the fetus that contains cells from the developing baby. Clinicians can use this to test for Angelman syndrome or other genetic disorders. To obtain a sample of the amniotic fluid, your doctor will insert a needle into the uterus through the abdomen.
The placenta is an organ attached to the lining of the uterus during pregnancy that contains the fetus and supports its development. It contains genetic material from both the fetus and the mother, so clinicians can use it to test the baby for genetic diseases.
To collect a small sample of the placenta, your doctor will insert a needle through the abdomen or the vagina, using it to “vacuum up” small finger-like projections called the chorionic villus. Clinicians can use these pieces for genetic testing.
CVS has a few advantages over amniocentesis: It shouldn’t puncture the placenta, and it can be performed earlier in the pregnancy than amniocentesis.
What are the risks of prenatal genetic testing?
Although rare, complications can occur during either procedure. These include bleeding, infection, and damage to the placenta or the fetus. There is also a very small risk that either method may cause a miscarriage.
Your physician will discuss the risks of these procedures with you, as well as any factors that may present more risk to you or your baby.
What happens after amniocentesis or CVS?
After doctors have collected the baby’s DNA using either method, he or she will send the sample to a laboratory for genetic testing. It may take a few days or weeks for the result to become available. After your doctor has received the results, he or she will discuss the findings from the test with you and your options moving forward.
Angelman syndrome and genetics
Angelman syndrome develops when a protein called UBE3A is missing in certain areas of the brain. This is because in some areas of the brain, only the maternal copy (the gene copy that a child receives from their mother) of the UBE3A gene is active.
There are several genetic reasons why UBE3A might be missing. For example, there may be a mutation in the maternal copy of the gene so cells cannot make the UBE3A protein, or make it with mistakes. Alternatively, chromosomal rearrangements can cause whole segments of the genome to be lost, including the portion containing the UBE3A gene.
Both of these causes of Angelman syndrome are detectable by genetic testing. Some other causes of Angelman syndrome (such as paternal uniparental disomy and imprinting errors) may require special genetic testing for detection. If you are concerned, you should discuss what genetic tests may be needed with your doctor and genetic counselor.
About 10% of Angelman syndrome cases have no known genetic cause. Prenatal genetic testing would not detect these cases.
Last updated: July 20, 2020
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