A human being is made up of cells that contain 23 sets, or pairs of chromosomes. Half of their chromosomes are from the mother, and half from the father. Sometimes it happens inside the cells that it causes a deviation in the number of chromosomes; sometimes there are too few chromosomes and other times even more.
Trisomy 18 is a chromosomal disorder in which there is an extra 18th chromosome in the body’s cells. In some cases, the third chromosome is present in all the cells of the body, while in others it is present only in part of the body’s cells. No matter how many cells are made in the body, Trisomy 18 is often fatal, as in fact in most pregnancies where a fetus has Trisomy 18 it results in miscarriage or abortion.
There are three different forms of Trisomy 18; Full Trisomy 18, Mosaic Trisomy 18 and Partial Trisomy 18. Full Trisomy 18, the most common form of this chromosomal disorder, is characterized by the presence of a third of the 18th chromosomes in every cell of the body. Mosaic Trisomy 18 is characterized by the presence of a third 18th chromosome in only one part of the cells. Partial Trisomy 18 is characterized by the presence of only a third of the 18th chromosomes in the cells.
Trisomy 18, or Edwards Syndrome can be diagnosed during pregnancy. There are special blood tests, which can be done “triple screen” or maternal serum alpha-fetoprotein. to determine the likelihood that the child has a disorder. This test is now being offered to mothers between 15 and 20 weeks pregnant. It is important to know that this test can help to determine whether there is a chance that the baby may have Edward’s syndrome , or another disorder genetics does not give a definitive outcome.
Ultrasound is another routine prenatal. During an ultrasound test, the doctor can determine whether there is a risk of the baby having Trisomy 18 by looking for details. Often babies who have Trisomy 18 have either too much or too little amniotic fluid around them in the womb. They can have two urns umbilical than three cords. There may be abnormalities in the children’s heart, kidneys, brain, or skeletal that suggest the possibility of a disorder. Again, this test can help determine whether or not there is a possibility of a baby having Edward’s Syndrome, it is not a definitive test.
To get definitive results, doctors must look at the chromosomes themselves. This can be done in two ways. It is important for the mother to know and understand the risks associated with these tests before they are done.
Amniocentesis, usually done anytime after 15 weeks of pregnancy, is a test in which doctors obtain a sample of amniotic fluid around the site. baby. There are some of the baby’s natural cells flowing through the amniotic fluid and these cells have been tested for genetics. – up This test is performed by doctors through a needle sticking to the lower abdominal wall and into the uterus to obtain fluid. They use ultrasound to help guide them and the procedure takes less than a minute. This test is known to cause miscarriage in about 1 out of every 300 pregnancies. Once this is done, the doctor will give the mother very specific instructions and limitations in order to decrease the chances of miscarriage. The accurate diagnosis of chromosomal disorders is very high with this test.
Another test available to get a definitive result is called Chronic Liver Sampling. This test is usually done between 10 and 12 weeks of pregnancy and takes a sample of the tissue that is in the mouth of the placenta itself. A long system of cells must be taken from the fetal part of the placenta to obtain cells that are the same as those of the child. To perform this test, an ultrasound will help the doctor guide the needle through the cervix or lower abdomen and into the placenta. A small portion of the cake is removed and used for testing. This test carries a minimal risk of miscarriage and also a small risk of causing specific organ failure in infancy. In about 3% of cases, this test presents difficulty in understanding the results and amniocentesis is required for a definitive result.
Although Edward’s syndrome is highly fatal and pregnancies end in miscarriage or abortion, babies with the disorder are still born alive. Many of these babies went through the entire pregnancy undiagnosed. In these cases, it is very common for a baby to be born with many health and physical abnormalities. Most of these babies will spend many hours in the neonatal intensive care unit, and many will undergo multiple surgeries. But most of these children will not live. Approximately 40% of newborns who have Trisomy 18 will survive the first week of life. That is 60% will not survive. By the age of one month, only 20% of all babies born with Trisomy 18 will survive, leaving 80% who do not survive. In six months only 6% will survive. Only about 5% of all babies born with Trisomy 18, or Edward’s syndrome, will live to see their first birthday. For those babies who are born with Trisomy or Mosaic or partial 18, the numbers are slightly higher, but the outlook is still grim. Those who survive beyond the first year of life will likely have many health problems and physical abnormalities.
There is no cure for Edward’s syndrome or Trisomy 18. The results that are diagnosed in a child vary greatly from one to another. Many babies are born, seemingly healthy, and die unexpectedly due to an unwarranted case of Trisomy 18. In these cases, there is never a definitive answer because chromosomal testing cannot be done accurately. Some babies are born with multiple health problems and/or physical abnormalities and don’t live long enough to be diagnosed. Others, however, are diagnosed with only mild problems and manage to live beyond their first birthday. There is no way of knowing how Trisomy 18 will affect the baby until the baby is born.
Sources for this article include:
http://www.trisomy18.org
http://www.novelguide.com
http://children.webmd.com/trisomy-18-syndrome
