EBN-Individuals with Down syndrome experience heart issues, hearing loss, and vision impairments, some of which can be treated if identified early and promptly before the condition worsens. Down syndrome is caused by a genetic disorder that causes abnormal chromosome division, which alters a person’s growth and physical characteristics and results in lifelong mental and developmental delays that vary from child to child.
Causes of Down syndrome during pregnancy:
Three different types of abnormal cell division that occur to chromosome 21 include:
- The first type is called Trisomy 21: It causes 90% of Down syndrome cases, as the extra chromosome develops in the egg or sperm during their development.
- The second type is Mosaic Trisomy 21. This is a rare condition that occurs in only 2% of Down syndrome cases . It occurs when chromosome 21 splits after fertilization, resulting in the total number of chromosomes in the cell becoming 47 instead of 46.
- The third type is Translocation Trisomy 21: a rare condition that occurs in 3-4% of people with Down syndrome, in which chromosome 21 is completely or partially attached to another chromosome.
Although a fetus with Down syndrome differs in many characteristics from a normal fetus, there is no difference in the fetus’s movement, heartbeat, or development of its various organs from that of a normal child.
How and when can parents know that they will have an affected child?
Some tests can be performed during the first trimester of pregnancy, during the first 12 weeks or after this period. There are two types of these tests. Prental
screening tests give an estimate of whether your fetus has Down syndrome or not and can be considered a preliminary step toward the second stage. Diagnostic tests are more accurate than screening tests, and doctors recommend that all pregnant women, regardless of their age, undergo these tests.
Screening tests
Combined test
It is performed during the first 3 months of pregnancy and includes measuring the levels of pregnancy-associated plasma protein A (PAPP-A) in the blood. If there is an abnormality in its level, this indicates the presence of a problem.
It also measures the level of the pregnancy hormone (HCG) in the blood. If there is an abnormality in its level, this indicates the presence of a problem.
An ultrasound test is performed on a specific area at the back of the fetu’s neck . If a large amount of fluid accumulates there, this indicates the presence of a problem with the pregnancy.
Integrated testing
It is performed during the first and second trimesters of pregnancy in two stages:
Stage 1: Performed during the first trimester, plasma protein A (PPA) levels and nuchal translucency testing are measured.
Stage 2: Performed during the second trimester, PPA levels are measured for four pregnancy-related substances: alpha-fetoprotein (AFP), plasma protein A (PPA), hCG, and estriol. The results of both stages are combined with information about the woman’s age to determine the fetus’s likelihood of having Down syndrome.
Diagnostic tests for Down syndrome
These tests are often a second step after screening tests as a form of confirmation. They are performed after a positive screening result. They involve taking a sample of placental cells
and genetically analyzing them, as these cells closely resemble fetal cells . This test is performed during the first three months of pregnancy and is a relatively safe test. Another option is
taking a sample of the fluid around the fetus during the second trimester of pregnancy. A sample of the amniotic fluid surrounding the fetus is withdrawn by inserting a needle into the mother’s uterus and genetically analyzed for any abnormalities.
It’s worth noting that in the case of in vitro fertilization, the fertilized egg can be genetically analyzed before implantation in the mother’s uterus. Therefore, in vitro fertilization is a good option for parents who have a high chance of having a child with Down syndrome.
