Dual Test Screening, 11-14. also known as the week screening test or the nuchal thickness test, this test is a screening test to detect babies with Down syndrome and a chromosomal abnormality called Trisomy 18 at a very early stage of pregnancy. No matter how old they are, all women have the risk of giving birth to a physically or intellectually disabled baby.
It is performed in infants with a head-to-butt distance(CRL) of 45-85 mm.
Although it is still small, these weeks are especially vital for the diagnosis of some structural disorders and chromosomal disorders, especially Down syndrome, dual test screening is important.
As with all screening tests, this test does not make a diagnosis. It indicates only babies who are at high risk of the disease and ensures that diagnostic tests are performed in these babies that lead to a definitive diagnosis. In other words, just as a high risk test does not prove that the baby has an anomaly, a low risk does not guarantee that the baby is completely healthy.
The following structures are taken into consideration;
Nuchal Thickness(NT): During these weeks, there is a physiologically millimetric fluid accumulation under the skin on the nape of all babies. The thickness of this liquid is measured. A significant increase in this thickness increases the risk of both chromosomal and structural disorders.
Nevertheless, a very significant part of the cases with increased nuchal thickness is normal. Although the limit value of the nuchal Decollete thickness varies according to the size of the baby, 3.5 mm and above is an increased measurement for every baby between these weeks.
The presence of a nasal bone: in about half of babies with Down syndrome, the nasal bone either does not develop at all or develops little.
Ductus venosus : Examination of the part of the vein that brings clean blood from the umbilical cord that passes through the baby’s liver before it reaches the right atrium of the heart using color doppler. Jul.
After the ultrasound, blood is taken from the expectant mother for a Double Test on the same day and the levels of two hormones secreted from the placenta, called free hCG and PAPP-A, are measured.
For the screening of Down syndrome and other common chromosomal disorders, a special risk assessment is made for this pregnancy by combining the above ultrasound findings, dual test values and maternal age in a computer program. As a result of this evaluation, the expectant mother is divided into a high or low risk group according to the limit value taken. This test, in which all the data are combined, is called a Combined Test.
If we can apply a definitive test (Amniocentesis-CVS) to all expectant mothers who fall into the high-risk group, it is possible to detect babies with Down syndrome by 90-95%. It should not be forgotten that if we want to know 100% whether a baby has Down Syndrome or not, we must definitely take a baby’s cell and examine it in the genetics laboratory. This is made possible either by taking a sample from the fluid around the baby (amniocentesis) or by performing a biopsy (CVS) from the placenta (baby partner). Since both interventions carry a certain risk of baby loss, they should only be applied to the increased risk group.
The first trimester screening results are given as positive or negative, as well as the probability that your risk of carrying a baby with Down syndrome is as high as 1/250.
Dual test screening correctly identifies about 85 percent of women carrying babies with Down syndrome. About 5 percent of women have a false positive result, which means that the test result is positive, but the baby does not actually have Down syndrome.
When evaluating your test results, keep in mind that the first trimester screening only shows your overall risk of carrying a baby with Down syndrome or trisomy 18. A low-risk outcome does not guarantee that your baby will not have one of these conditions. Likewise, a high-risk outcome does not guarantee that your baby will be born with one of these conditions.
If your test result is positive October, additional tests will be required. For example:
Prenatal cell-free DNA (cfDNA) screening: This test is an advanced blood test that examines fetal DNA in the mother’s bloodstream to determine whether your baby is at risk of Down syndrome, trisomy 13, or trisomy 18. Some forms of cfDNA screening also screen for other chromosome problems and provide information about fetal sex. A normal result can eliminate the need for a more invasive prenatal diagnostic test.
Chorionic villus sampling (CVS): CVS can be used to diagnose chromosomal conditions such as Down syndrome. Throughout CVS is usually done in the first trimester, a tissue sample is taken from the placenta to test. CVS carries a small risk of miscarriage.
Amniocentesis : Amniocentesis can be used to diagnose chromosomal conditions such as Down syndrome and neural tube defects such as spina bifida. A sample of amniotic fluid is taken for testing during amniocentesis, which is usually performed in the second trimester. Like CVS , amniocentesis also carries a small amount of low risk.
Working from a limited surface negatively affects the quality of the examination and the result. Come to the review in comfortable, easy-to-move clothes. Especially jeans with a belt attached complicate the preparation process.
The specialist who conducts the examination should work very carefully and in a certain discipline. Therefore, please;
Turn off your mobile phone or put it in silent mode.
Do not Deconstruct conversations among yourselves.
Follow up with your questions related to pregnancy, but which will not have an effect on the examination, and ask your doctor.
Bring only one companion with you.
Do not bring children to the examination.
No. The device works with sound waves. No increased anomaly rate due to ultrasonography has been reported in comparative studies conducted up to this time. However, it should not be applied too often unless necessary.
A very important part of the review is black-and-white (2D). The only ‘color’ concept we used in this review is ‘color doppler’, in which we examine the blood flow in the vessels. But the definition of ‘color ultrasonography’ among the people is used instead of 3-Decimated or 4-dimensional (3D/4D) ultrasonographic examination. The device we are using is an advanced device with 3D/4D capability. For this reason, the 2D sectional quality, which is important for us, is at a high level and facilitates the examination we do.
If images can be taken in appropriate sections, we can have an idea of the baby’s gender. The accuracy rate of the gender prediction made during the examination conducted during this period is about 75%.
Mostly no. According to the position of the uterus and placenta, your doctor will inform you if it is necessary to be cramped to urinate.
abdominal ultrasonography is sufficient for 11-14 week screening in 90% of pregnant women. But in the remaining part, vaginal ultrasonography may be required due to the structure of the mother’s abdomen and uterus or the position of the baby.
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