Chorionic Villus Sampling
The diagnostic procedure of taking out a sample tissue (Choroinic Villi) from the placenta to detect congenital abnormalities in a fetus is known as Chorionic Villus Sampling (CVS). With the guidance of ultrasound, the position of placenta is first determined. There are two methods - trans-cervical and trans-abdominal to perform this test. The position of the placenta helps the physician choose a suitable method. For trans-cervical CVS, parameters like the position of the uterus, the size of the gestational sac and the position of the placenta inside the uterus are first determined using abdominal ultrasound. Using a good antiseptic, the vulva, vagina and the cervix are cleansed. The abdomen is also cleansed for trans-abdominal procedure.
Trans cervical procedure: A thin plastic tube is inserted through the vagina and cervix for the trans-cervical procedure to reach the placenta. A tiny sample of chorionic villus tissue is taken out after locating the exact position of the placenta.
Trans-abdominal procedure: This procedure is similar to the earlier one, but a needle is inserted through the abdomen in this test to reach the uterus and then to the placenta. The chorionic villus sample tissue is drawn into the syringe, while the needle is guided by ultrasound.
This sample is then taken to the laboratory for evaluation. This procedure can be conducted even earlier than amniocentesis to detect any congenital defects present in the fetus. It is done at around 10 to 12 weeks after the last menstruation. Study of the DNA, chromosomes and enzymes of the fetus can be conducted using the sample taken out during the test. Results are available within a week or two. If there are any abnormalities found in the fetus, it is easy to conduct a therapeutic abortion, in case it is necessary. Pregnant women over the age of 35 who are at risk for giving birth to a baby with Downs Syndrome or those who have had birth defects in an earlier pregnancy are advised this test. For detecting neural tube defects and the Rh-incompatibility, amniocentesis is a better option. Hemoglobinopathies and Tay-Sachs disease can be detected through Chorionic Villus Sampling.
The risk involved in using CVS is slightly higher when compared to amniocentesis. Some complications like rupture of the amniotic membrane, miscarriage, infection, bleeding, Rh-incompatibility in the mother if she is Rh-negative and contamination of the sample with maternal cells can occur. When CVS is performed after 10 weeks of gestational period, there is a risk for limb defects in the fetus. If the mother's blood is Rh-negative, she has to receive RhoGAM to avoid Rh incompatibility. After the CVS, it is advised to have an ultrasound done after about two or four days to ensure the fetus is fine.
Down Syndrome
Down Syndrome is a condition where a person is born with 47 chromosomes instead of the usual 46. This additional chromosome leads to deviations in the way the brain and body develops. The risk of having a child with Down syndrome increases with the age of the mother. It is not an inherited condition except in the case of Translocation Down syndrome. This birth defect reflects in children with delayed development. At birth, children with Down syndrome might have birth defects of the heart and eye problems. As they grow, there is short attention span and slow learning. Hypothyroidism and obesity are other characteristics feature of most persons suffering Down syndrome. Most people with Down syndrome have an abnormally shaped small head. There is a flattened nose and upward slanting eyes. Other recognizable symptoms of a person suffering Down syndrome are reduced muscle tone and short hands with stubby fingers.
After birth, blood tests help in checking for the additional chromosome. Such children have a single crease across the palm. ECG and x-rays of the chest and the gastrointestinal tract are also done to confirm the diagnosis of Down syndrome. Surgery is often done in cases where there is gastrointestinal blockage or heart defects. In some cases, Down syndrome is diagnosed during the gestation period. Ultrasound and amniocentesis and Chorionic Villus Sampling can diagnose Down syndrome in the fetus during pregnancy.
Parents of children with Down syndrome can join support groups that helps in connecting with people who have experience in dealing with this condition. Children suffering Down syndrome need special education that includes speech therapy, physiotherapy and mental health care. Massage helps in promoting wellbeing. Occupational therapy helps people with Down syndrome to live more independently; to manage their own dressing and feeding. A nutritionist can help in suggesting a well-balanced diet so as to control weight. Regular checkups with an ophthalmologist and auditory specialist aids in treating problems. The health of children with Down syndrome must be closely monitored.
Genetic testing
Genetic testing is a method of genetic diagnosis to check for the susceptibility to hereditary diseases and can also be used to establish the ancestry of any person. Genetic testing studies the chromosome, breaking it to individual genes. In a broader sense, it can be used as a biochemical test for scrutinizing the existence and nonexistence of main proteins that hint abnormalities of certain genes. Genetic testing studies the abnormality in the chromosomes, genes or proteins. It can be used to find out whether a particular genetic condition is developing and it's chances of being passed over to the future generations.
The most widely used type of genetic testing is newborn screening. Genetic testing during pregnancies is called as prenatal genetic testing and is performed during pregnancy to screen or identify birth defects. This provides ample information on the developing fetus both for the parents and the physician. Amniocentesis and chorionic villus sampling is the common diagnostic test performed to diagnose any defect in the fetus. These diagnostic tests are ordered for if the triple test (AFP test, hCG blood test, and UE3) returns abnormal results.
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