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During pregnancy, a number of tests are performed to understand the abnormalities in the baby. As a result of these tests, discomfort in the baby can occur and early measures can be taken. American Hospital Women's Health Unit Chief Dr. Contact Bülent directly It gives information about the tests performed during pregnancy.
Tests to detect possible chromosomal abnormalities during pregnancy can be examined in two groups. The first of these is Amniocentesis, which allows for definitive diagnosis, and ultrasound and biochemical tests that show changes in age-dependent risk.
Every woman is at risk of chopping babies with chromosomal anomalies at any age. The most common of these anomalies is Down syndrome (Mongolism) and its incidence increases with advancing age. Down syndrome is a congenital disease caused by the fact that chromosome 21 is trisomy, not 2, and it is accompanied by retardation and sometimes other body abnormalities. The risk of carrying a baby with Down syndrome increases significantly from the age of 35 and rises above the risk of amniocentesis (1/200). For this reason, amniocentesis is recommended as a classic for mothers who have been 35 years of age at the time of delivery. The risk of Down syndrome is increased mathematically in mothers who have twin pregnancies due to having two babies. The age at which amniocentesis should be performed in twin pregnancies is accepted as 31 years.
In recent years, the sensitivity of screening tests has increased and especially 11-14. The measurement of nuchal translucency and presence of nasal bone during gestational weeks increased the likelihood of recognizing infants with Down syndrome without performing amniocentesis. The necessity to perform amniocentesis has shifted to older ages and it is now decided to be decided by looking at screening tests for all ages. 11-14 weeks screening test and in some cases between 16-18 weeks II. In women with normal trimester screening and without any markers associated with Down syndrome on ultrasound, the risk is very reduced but not zero. Amniocentesis may not be performed in women over 35 years of age with these characteristics. Especially under the age of 38, this practice is becoming more common. The decision not to have amniocentesis should be made by the mother and father. Physicians are only guiding and do not undertake the decision of amniocentesis as medico-legal (for medical-legal reasons). There is a risk of healthy infant loss in those who have undergone amniocentesis and those who do not have an infant with Down syndrome. These risks should be balanced by the test risk and discussed with their physician and then decided by the couple.
First trimester screening test (dual test or 11-14 weeks test):
This test has two parts. The first is ultrasound to measure the thickness and height of the baby's nape. These measurements are made by vaginal or abdominal ultrasound. During the ultrasound measurements, the baby's nasal bone is also examined. The risk of Down syndrome is calculated by measuring PAPP-A and free beta-hCG in the blood within 24 hours of the measurements. It should not be forgotten that Down syndrome screening tests during pregnancy show whether age-related risk increases rather than making a definitive diagnosis. It is reasonable to perform amniocentesis if the age-related risk increases and the risk of amniocentesis increases.
Second trimester screening test (triple test or 16-18 weeks test): This test is used to calculate risk by measuring AFP, hCG, and estriol in the blood. AFP also scans the spinal bifida of the spine, called a neural tube defect. Before the test, the head measurements of the baby should be made with an ultrasonography to ensure the gestational age. Amniocentesis may be performed when the test risk exceeds the risk of age-dependent Down syndrome, especially if it exceeds 1/250.
Sampling of the fluid surrounding the baby. It is done between 16-18 weeks. It is called early amniocentesis and it is called as 12-14. However, the procedure is not preferred since it is followed with higher infant loss rates. Amniocentesis is a very simple procedure without anesthesia. First, the location of the baby and placenta is determined by ultrasound. Then, under ultrasound observation, a small needle is inserted into a fluid pocket away from the baby and placenta and approximately 20cc of amniotic fluid is removed. When the placenta is in the anterior wall, it may be inevitable to pass through the placenta. There is no evidence that this increases infant loss. It is normal for some bleeding to occur in the gestational sac from where the needle passes. This bleeding stops spontaneously. There may be slight cramps after the procedure. These are usually short-term. Rarely, there may be a slight discharge due to amniotic fluid leak. Activity should be avoided for 24 hours after the procedure.
Genetic examination of amniocentesis fluid:
The liquid taken is sent to the genetic laboratory. There are two parts of genetic analysis. First, FISH test is performed to screen for the most common chromosomal abnormalities (21,18,13, X, Y). FISH test is 95% reliable and results are obtained within 48-72 hours. The results of karyotype determination showing all chromosome formation are obtained within 2-3 weeks and are 100% reliable.
What should be done if amniocentesis results are abnormal?
If the result shows a baby with a chromosomal abnormality, it is usually a miscarriage. Rarely do mothers who want to carry and deliver a baby with Down syndrome. However, it is generally desired to terminate the pregnancy.