Some expectant mothers want to know whether their babies are normal or not before birth. Some pregnant women do not want tests during pregnancy because they will not allow the pregnancy to be terminated even if there is an abnormality in the baby. As physicians, we may request detailed genetic tests to identify babies who will need treatment, especially immediately after birth. For example, in the case of a diaphragmatic hernia where the intestines are inside the chest cavity, knowing the problem in advance is necessary to ensure the possibility of surgery on the baby immediately during birth.
However, genetic examination is expensive. Genetic disorders are so rare that it is not economically possible to examine every pregnant woman. Relatively inexpensive screening tests have been developed to screen all pregnant women. However, unfortunately, their reliability is not high. For example, 50% of genetic abnormalities are missed by routine ultrasonography (large abnormalities are much less likely to be missed. Missed abnormalities are usually small or difficult to recognize, and fortunately, they occur in very rare disease cases.
Genetics research methods, amniocentesis
Examination of the prospective mother and father: Families with a high probability of having a genetic disease in the family are examined by clinical geneticists, and if necessary, chromosome maps of the prospective mother and father are prepared. Once a genetic disease is detected, its transmission rates to children and prenatal diagnosis opportunities, if any, are discussed. The older age of the mother and even the father increases the likelihood of genetic diseases being seen in the baby.
Ultrasonography: Many major diseases. The baby can be diagnosed with ultrasonography before the baby is 14 weeks old. If there is a vital problem, this week is the appropriate week for miscarriage. In doubtful cases, amniocentesis is performed.
Triple test: This is the alpha-fetoprotein in the mother's blood. It is a test that measures the levels of three hormones called , b-hCG and estriol and compares them with the hormone values in thousands of women via a computer. In particular, the development of the brain-nervous system, Down syndrome (3 chromosomes 21 instead of 2), and the risk of trisomy 18 (one extra chromosome 18) are determined in the baby. If the risk is high, more detailed analyzes (for example, amniocentesis) may need to be performed. The point that should not be forgotten is that this test should only be used to estimate risk. Diagnosis cannot be made.
Chriocentesis: A small piece of the baby's placenta (partner) is taken with the help of a needle. Fetal tissues are separated and genetic research is performed using these tissues. Chromosome mapping can be done immediately within 3-4 hours. Another advantage is that genetic diagnosis can be made early, when the pregnancy is 10 weeks old.
Amniocentesis: About 15-20 ml of the baby's fluid is taken. The procedure is usually performed between 12-20 weeks. Its disadvantage is that it requires a long time (7-15 days) since the cells in the collected fluid must be produced in the laboratory.
Cordocentesis: This method is used in later stages of pregnancy (after 20 weeks). Some blood diseases can be diagnosed by examining the blood sample taken from the umbilical cord and sometimes directly from the body. It is also a technique used to prevent infant deaths due to blood incompatibility.
Fetal leukocytes in maternal blood: In general, the placenta (partner) prevents the mother's and baby's blood from mixing. However, some of the baby's blood cells pass into the maternal circulation. These cells live in the mother's blood for a long time. It is even found in the mother's blood many years after the child is born. These cells can be separated and some genetic problems can be solved using some very sensitive methods (PCR). For example, gender determination may be possible at a very early stage. It is a method that is not yet widely used in the research phase.
Fetoscopy: An optical instrument such as a very thin needle (such as laparoscopic instruments) is inserted directly into the uterus through a thin incision made in the mother's womb. The baby is displayed in the water-filled sac in which it floats. Photos can be taken. It can be done after the 16th week. It is performed less and less because of its risk for the baby (3-5% baby loss) and with the development of other less invasive methods.
Situations Where Detailed Genetic Research Should Be Performed
Pregnant women aged 35 and over
There is a risk of loss of pregnancy when amniocentesis is performed for pregnant women older than 35 years of age. Skies are lower than the risk of fetal anomalies and especially the risk of giving birth to a child with DOWN SYNDROME. For this reason, amniocentesis is recommended.
There are some genetic diseases in the family (Mongolian child-Down Syndrome, etc.)
Some genetic diseases are the reason for frequent marriages within the family. It is observed more frequently in some ethnic groups. Sickle cell anemia is more common in people of African, Mediterranean, Middle Eastern, Caribbean, Latin American or Indian origin. Tay-Sachs disease is common in Ashkenazi Jews.
Retarded child in the family
Down syndrome (Mongolism) and Fragile-X syndrome are the most common diseases associated with mental retardation. They are two genetic diseases. However, mental retardation due to chromosomal anomaly is responsible for 35-40% of all mental retardation problems.
A family history of genetic disease for which genetic examination is possible
Some Prenatal diagnostic tests have been developed for diseases. Tay-Sachs, cystic fibrosis, Down syndrome, thalassemia, and sickle cell anemia are among the most common ones.
Familial genetic abnormality that can be recognized by ultrasound
Congenital heart diseases, polycystic kidneys, Potter's syndrome and some congenital diseases can be diagnosed by prenatal ultrasonography. On the other hand, club foot, cleft palate, cleft lip and some minor heart diseases (even though they can be diagnosed ultrasonographically) are often overlooked.
Previous stillbirth, recurrent miscarriages or Second Cycle. Child deaths in the trimester (3-6 months period)
Such problems are often caused by trisomies and Potter syndrome (hereditary kidney development problem).
Parents Close kinship between candidates
Any close kinship increases the likelihood of genetic diseases occurring in children.
In case the mother has diabetes, phenylceneuria or epilepsy
These diseases should be controlled before pregnancy. Otherwise, disabilities may occur in the baby.
If any of the parents have a disorder in blood clotting
Hereditary hemoglobin disorders or some hereditary blood diseases may occur in the baby's womb for 4-6 months. It can cause death in pregnant women.
Some drugs taken at the beginning of pregnancy
Some antibiotics, epilepsy drugs, drugs affecting blood clotting, hormones, steroids, cancer drugs
p>Drinking alcohol or narcotic drugs during pregnancy
A condition called fetal alcohol syndrome occurs in children of mothers who drink excessive alcohol. Taking some sedatives or narcotic drugs along with alcohol can also cause the same problem.
Down Syndrome
It is a hereditary disease. Normally, human cells have 23 pairs of chromosomes. If chromosome number 21 has 3 instead of the normal 2, it creates a number of disorders that are usually accompanied by mental retardation. Trisomy 21, Mongolism, Down syndrome are other names. In the picture above you can see the typical facial expression of such a child.
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