Down syndrome is a genetic disease, which occurs very early in pregnancy, by the time your baby is forming. People normally have 23 pairs of chromosomes. However, people with Down syndrome have another pair of chromosomes 21.
Prenatal screening tests for Down syndrome can be performed during the first and second trimester (Read also: First Week of Pregnancy). These tests only try to identify the risk of your baby suffering from Down syndrome. If these tests show that your baby has an increased risk for Down syndrome, further tests are necessary to confirm the diagnosis.
There are two types of tests available for prenatal screening for Down syndrome during the first trimester. Ultrasound scan is combines with blood tests. The dating scan can be performed between the 8th and 14th week of pregnancy, while the nuchal translucency scan can be performed between the 11th and 13th week of pregnancy. There is always the possibility of performing these tests at once, both the dating scan and the nuchal translucency scan between the 11th and 13th week of pregnancy. The blood test is performed usually between the 9th and 12th week. With the help of blood tests, the level of pregnancy hormones is measured. During a normal pregnancy, these hormones are increased, while in cases of any genetic problem, these hormonal levels are abnormal.
All the information gathered from these three tests is combined also with your age in order to determine the risk and chances of having a baby with Down syndrome.
During the second trimester another prenatal screening test for Down syndrome is available. This test is known as the triple test, which measures the proteins associated with pregnancy. The information gathered from this test is combined with your age in order to determine the risk and chances of having a baby with Down syndrome. The triple test is usually performed between the 14th and 20th week of pregnancy.
Once the tests performed during the first and second trimester show that there is a possible risk of having a baby with Down syndrome, further diagnostic tests are available. The diagnostic tests include: amniocentesis, chorionic villus sampling and cordocentesis.
Amniocentesis is a procedure during which a sample of the amniotic fluid is collected. The collection of the amniotic fluid is then used to analyze the fetal chromosomes. It is usually performed after the 15th week of pregnancy and there is a slight risk of miscarriage.
Chorionic villus sampling is a procedure during which cells are taken from the placenta. It is typically performed after the 10th week of pregnancy and there is also a slight risk of miscarriage.
Cordocentesis is also known as percutaneous umbilical blood sampling, during which the fetal blood is collected from a vein in the umbilical cord. This collected blood is then examined for chromosomal defects. This test is performed during the 18th and 22nd week of pregnancy. Cordocentesis has a greater risk of miscarriage than amniocentesis or chorionic villus sampling.
It is always difficult to handle the fact that something might be wrong with the pregnancy and the development of the baby, not to mention when there is a possibility of a genetic disease.
Dmitry Bronfman, MD, is a board-certified gynecologist who specializes in all aspects of contemporary women’s health, preventive medicine, pelvic pain, minimally invasive and robotic surgery, and general, adolescent, and menopausal gynecology.
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