What is a Dual Screening Test ?
Dual screening test, 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. Regardless of how old they are, all women are at risk of giving birth to a baby with physical or intellectual disabilities.
It is performed on babies with a head-to-butt distance(CRL) of 45-85 mm.
Although it is still small, these weeks are especially important for the diagnosis of some vital structural disorders and chromosome disorders, especially Down syndrome.
As with all screening tests, this test does not make a diagnosis. It points only to babies at high risk of the disease and allows diagnostic tests to be performed in these babies that lead to a definitive diagnosis. In other words, just as the fact that the test shows a high risk is not proof that the baby has an anomaly, the fact that the risk is low does not guarantee that the baby is completely healthy.
How is the Dual Screening Test applied?
The following structures are taken into consideration;
Heart activity, baby movements
Placenta(baby partner) localization, the amount of water the baby is in
Growth tracking by measuring the head-butt distance
Head-body integrity
Formation of head bones and intracranial structures
Front and back body lines
Observation of two arms and two legs
Stomach, bladder
Reminders of the Importance of Dual Screening Test Examination
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 belted jeans make the preparation process difficult.
The expert who conducts the examination must work very carefully and within a certain discipline. Therefore, please;
Turn off your mobile phone or put it on silent mode.
Do not chat among yourselves Decently.
Follow up with your pregnancy questions that will not affect the examination, but ask your doctor.
Please bring only one companion with you.
Do not bring children to the examination.
Measurements Made During the Dual Screening Test
Nape Thickness(NT)
During these weeks, all babies have a physiologically millimetric accumulation of fluid on the nape of the neck, under the skin. 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 are normal. Although the nape thickness limit value varies depending on the size of the baby, 3.5 mm and above is an increased measurement for each baby between these weeks. Dec.
The presence of the nasal bone
In about half of babies with Down syndrome, the nasal bone either does not develop at all or underdevelops.
Ductus venosus
Examination of the vessel that brings clean blood from the umbilical cord using color doppler of the part of the heart that passes through the baby’s liver before it reaches the right atrium. Jul.
After the ultrasound, blood is taken from the expectant mother for a Double Screening Test on the same day, and the levels of two hormones called free hCG and PAPP-A secreted from the placenta are measured.
To screen for Down syndrome and other common chromosomal disorders, the above ultrasound findings, dual test values and maternal age are combined in a computer program to conduct a risk assessment specific to this pregnancy. As a result of this evaluation, the expectant mother is divided into high or low risk groups according to the received limit value. 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, we must definitely take a cell belonging to the baby and examine it in the genetic laboratory.
This is 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.
How are the Dual Screening Test Results Evaluated ?
The first trimester screening results are given as positive or negative, as well as your risk of carrying a baby with Down syndrome as a probability of 1/250.
The 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 actually does not have Down syndrome.
When evaluating your test results, remember that a first trimester scan 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, additional tests will need to be performed. Oct. 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 may 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. During CVS is usually performed during 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 carries a low risk to a small extent.
Frequently Asked Questions About the Dual Screening Test
Will Ultrasonography Harm the Baby?
No. The device works with sound waves. An increased rate of anomalies due to ultrasonography has not been reported in comparative studies conducted until this time. However, it should not be applied too often unless necessary.
Will the Review Be in Color?
A very important part of the review is black-and-white (2D). The only ‘color’ concept we use in this study is the ‘color doppler’, where we examine the blood flow in the veins. But among the public, the definition of ’color ultrasonography’ is used instead of 3-Dec 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 section quality, which is important for us, is at a high level and facilitates the examination we do.
Will the Gender of the Baby Be Determined?
If the image can be taken in the appropriate sections, we can have an idea of the baby’s gender. The accuracy rate of the gender estimate made in the examination conducted during this period is about 75%.
Do I Need to Be Cramped For Urine?
Mostly no. Your doctor will inform you if it is necessary to be tight in the urine according to the position of the uterus and placenta.
Will The Examination Be Conducted from Your Wife?
abdominal ultrasonography is sufficient in 90% of pregnant women to scan at 11-14 weeks. 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.
Dual Screening Test Prices 2026
You can contact us immediately to get information about dual screening test prices 2026.
Dr.Abdullah Jawahir
Radiology Specialist
Hekimoglu Imaging and Diagnostic Center