Nt scan timing
First Trimester Ultrasound and Nuchal Translucency – San Diego Perinatal Center
First trimester ultrasound performed between 11 and 14 weeks is an important early assessment of your pregnancy. This scan can be used to accurately date your pregnancy, to evaluate abnormalities in your ovaries and cervix, to accurately determine chorionicity in twins, to assess for placental abnormalities and to perform a nuchal translucency screen. In addition, at San Diego Perinatal Center, with our high resolution equipment, we are able to detect 40% of major fetal anomalies such as neural tube defects, abdominal wall defects, renal, limb and cardiac abnormalities on this early scan.
Nuchal translucency/First trimester screening – this blood test screens for Down Syndrome (Trisomy 21) and Trisomy 18. It is part of the California Prenatal Screening Program and is a free service to all pregnant women. Additional testing and counseling would be recommended if the test is positive. This test has about an 85 % detection rate for Down Syndrome.
Nuchal Translucency Screening for Detecting Trisomy 21 (Down Syndrome) and Trisomy 18.
During development of the embryo, there is a clear space beneath the skin at the back of the neck which we call the nuchal translucency. Between 11 and 14 weeks of pregnancy, this space can be measured by ultrasound and the size of this space is associated with the risk for fetal chromosome abnormalities and the risk for fetal heart defects. We use this measurement as an early screening tool to identify pregnancies at higher risk for these conditions.
If we can accurately measure the nuchal translucency, then a computer program can be used to calculate the risk for Down Syndrome and Trisomy 18 using the mother’s age and blood hormone markers. Women who screen positive at increased risk would then be offered further testing. The nuchal translucency screen will identify 85-90 percent of Down syndrome cases and 80-85 percent of Trisomy 18 cases.
Approximately 5-10% of the time, we are unable to obtain this measurement either because the baby does not cooperate or there are other technical factors like abdominal wall scarring, fibroids or maternal obesity.
In the State of California, there is a prenatal screening program which is used for risk calculations. The state requires that all first and second trimester blood specimens are performed in the state laboratory system. https://www.cdph.ca.gov/Programs/CFH/DGDS/Pages/pns/
It is important to realize that the only way to be certain that a baby does not have a numeric chromosome abnormality like Down syndrome is by means of Amniocentesis or Chorionic Villous sampling.
Risk for Other Birth Defects
The nuchal translucency measurement is more than just a screening for Down syndrome. A very small nuchal translucency measurement – less than 2.5 mm – places the pregnancy in a low-risk group for problems, such as fetal heart abnormalities.
Pregnancies where the nuchal translucency measurement is between about 2.5 and 3.5 mm are in an intermediate-risk group, and for these women, a genetic sonogram at about 18 weeks into the pregnancy plus a detailed sonogram of the heart (called a fetal echocardiogram) at about 22 weeks are recommended. Women with a nuchal translucency measurement of 3.5 mm or more have pregnancies at increased risk for chromosome problems, for abnormalities of the fetal heart, and for other birth defects, ranging from abnormalities of the skeletal system to the baby’s diaphragm. For these pregnancies, genetic counseling and a genetic sonogram at 18 weeks, and a fetal echocardiogram and a detailed scan at about 22 weeks, are recommended.
In the past, sonography at 11 to 14 weeks was not an effective way to screen for birth defects of the baby. The embryo at that stage was just too small to evaluate well. As time has gone on, the ultrasound equipment and our ability to interpret the images have both improved.
Now, at the 11 to 14-week scan, we are able to identify many major central nervous system, cardiac, abdominal, and limb abnormalities. Our center’s goal is to identify 40 percent of major structural malformations at the time of the nuchal translucency scan.
When is the best time to schedule a nuchal translucency scan?
The accuracy is highest when the lab work is done between 10 and 11 weeks into the pregnancy, and we recommend scheduling the nuchal scan between 12 and 13 weeks. As long as the lab test has been done more than a week before, we should be able to provide you with the Down syndrome and trisomy 18 risk calculations at the time of your ultrasound scan.
Nuchal translucency test Information | Mount Sinai
Nuchal translucency screening; NT; Nuchal fold test; Nuchal fold scan; Prenatal genetic screening; Down syndrome - nuchal translucency
The nuchal translucency test measures the nuchal fold thickness.
This is an area of tissue at the back of an unborn baby's neck. Measuring this thickness helps assess the risk for Down syndrome and other genetic problems in the baby.
How the Test is Performed
Your health care provider uses abdominal ultrasound (not vaginal) to measure the nuchal fold.
All unborn babies have some fluid at the back of their neck. In a baby with Down syndrome or other genetic disorders, there is more fluid than normal. This makes the space look thicker.
A blood test of the mother is also done. Together, these two tests will tell if the baby could have Down syndrome or another genetic disorder.
How to Prepare for the Test
Having a full bladder will give the best ultrasound picture. You may be asked to drink 2 to 3 glasses of liquid an hour before the test. DO NOT urinate before your ultrasound.
How the Test will Feel
You may have some discomfort from pressure on your bladder during the ultrasound.
The gel used during the test may feel slightly cold and wet. You will not feel the ultrasound waves.
Why the Test is Performed
Your provider may advise this test to screen your baby for Down syndrome. Many pregnant women decide to have this test.
Nuchal translucency is usually done between the 11th and 14th week of pregnancy. It can be done earlier in pregnancy than amniocentesis. This is another test that checks for birth defects.
Normal Results
A normal amount of fluid in the back of the neck during ultrasound means it is very unlikely your baby has Down syndrome or another genetic disorder.
Nuchal translucency measurement increases with gestational age. This is the period between conception and birth. The higher the measurement compared to babies the same gestational age, the higher the risk is for certain genetic disorders.
The measurements below are considered low risk for genetic disorders:
- At 11 weeks -- up to 2 mm
- At 13 weeks, 6 days -- up to 2.8 mm
What Abnormal Results Mean
More fluid than normal in the back of the neck means there is a higher risk for Down syndrome, trisomy 18, trisomy 13, Turner syndrome, or congenital heart disease. But it does not tell for certain that the baby has Down syndrome or another genetic disorder.
If the result is abnormal, other tests can be done. Most of the time, the other test done is amniocentesis.
Risks
There are no known risks from ultrasound.
Driscoll DA, Simpson JL. Genetic screening and diagnosis. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 10.
Walsh JM, D'Alton ME. Nuchal translucency. In: Copel JA, D'Alton ME, Feltovich H, et al, eds. Obstetric Imaging: Fetal Diagnosis and Care.
2nd ed. Philadelphia, PA: Elsevier; 2018:chap 45.
Last reviewed on: 3/31/2020
Reviewed by: John D. Jacobson, MD, Professor of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda Center for Fertility, Loma Linda, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Scanning Microsoft Windows systems
Windows Management Instrumentation ( WMI ) is Microsoft's implementation of the Web-Based Enterprise Management (WBEM) standard for Microsoft Windows operating systems. WMI is a standard set of interfaces for accessing devices, applications, and settings in the Windows operating system.
Using WMI technology, TNI obtains software, hardware, and computer registry data.
There are three methods for scanning Windows devices.
How it works
- The executable file tniwinagent.exe is downloaded to the remote computer in the administrative shared folder admin$ is an agent.
- The TNI Master module connects to the remote computer's Service Manager and installs and starts the agent as a service.
- The agent scans the computer, saves the collected information to a compressed file, and stops.
Weaknesses
- Significant traffic is generated.
- The scanning speed may drop if the connection is slow.
- Since the main module does all the data processing, when scanning large networks, the program consumes system resources noticeably.
Requirements for the computer being scanned
CPU 500 MHz RAM 64 MB 0035 Place on the disk10 MB TCP Ports 135, 445 and random ports above 1024 Windows (WMI)
Remote Call procedure 9000 9003 RPC
TCP/IPWindows version
2000, XP Pro, Vista, 7, 8, 8. 
1, 10, Server 2000/2003/2008/2012(incl. R2)/2016/2016 903 903 903 903 903 903 903 How it works
- The agent executable tniwinagent.exe is manually copied to the target computer and launched. Upon completion, the agent creates a file with the collected data.
- The received data file is manually moved to the TNI storage.
Optional
The agent can be started by a domain logon script, task scheduler, or startup.
Agent command-line options tniwinagent.exe :
-
/path:"\\server\path"- allows you to specify the path to the folder where the data file will be placed; -
/delay:XX- allows you to set a delay in seconds before the start of scanning; -
/overwrite- overwrite the data file if the folder already contains its older version.
See Manual Scan section for more details.
Requirements for the computer being scanned
Online scanning methods (on demand) generate network traffic:
Method on a remote computer from a remote computer
(UPLOAD)
(Download) 90006. 
3 MB 0.05-0.1 MB RPC 10 MB 18 MB Tigores in the table-average downtime etc.).
High traffic during RPC scanning is a result of obtaining data from the registry via WMI and depends on the number of applications and services installed on the remote computer.
In manual scan mode, as well as remote scan via SMB protocol, TNI installs a third-party driver to collect low-level hardware data, such as memory module information from SPD, S.M.A.R.T. hard drives, etc. In normal mode, the driver is installed and removed with each scan, which takes only a fraction of a second.
There are known issues with the Intel storage driver (iastor.sys) where a bug in that driver causes a blue screen during a low-level disk subsystem scan. TNI attempts to work around this issue by skipping a disk subsystem scan when it detects a loaded Intel storage driver. This behavior can be changed in the application settings or using the agent's command line switches.
Total Network Inventory
- Accounting for computers
- Software inventory
Network inventory, accounting for computers and software for corporate networks of various sizes.
What you learn from an NT scan during pregnancy
If you have recently found out you are pregnant, you will have several doctor visits and check-ups before your baby is born. Prenatal screenings can reveal health problems such as anemia or gestational diabetes. Screening can also monitor the health of your unborn child and help identify chromosomal abnormalities.
Pregnancy screening is done in the first, second and third trimesters. First trimester screening is a type of prenatal testing that gives your doctor early information about your baby's health, namely your baby's risk of chromosomal abnormalities.
An occipital translucency (NT) scan checks your child for these abnormalities. This test is usually given between 11 and 13 weeks of pregnancy.
What is the purpose of an NT scan?
The NT scan is a common screening test done during the first trimester of pregnancy. This test measures the size of the transparent tissue, called the nuchal space, at the back of your child's neck.
It is not unusual for a fetus to have fluid or a clear space in the back of the neck. But too much free space can indicate Down syndrome or another chromosomal abnormality such as Patau syndrome or Edwards syndrome.
The cells in our body are made up of many parts, including the nucleus. The nucleus contains our genetic material. In most cases, the nucleus has 23 pairs of chromosomes, which are equally inherited from both parents.
People born with Down syndrome have an extra copy of chromosome 21. Down syndrome, which cannot be cured, causes developmental delay and various physical characteristics.
They include:
- short
- eyes tilted up
- low muscle tone
This condition affects 1 in every 700 babies born in the United States.
This is one of the most common genetic conditions. Patau syndrome and Edwards syndrome are rare and often fatal chromosomal abnormalities. Unfortunately, most children born with these anomalies die within the first year of life.
When is an NT scan scheduled during pregnancy?
The space at the back of the neck of a developing baby may disappear by 15 weeks, so an NT scan should be done in the first trimester.
This test may also include a blood test to measure plasma protein and human chorionic gonadotropin (hCG), a maternal hormone. Abnormal levels of any of these may indicate a problem with the chromosome.
How does NT scanning work?
Your doctor or technician will perform an abdominal ultrasound during the screening. Alternatively, you can have a transvaginal test, in which an ultrasound probe is inserted through the vagina.
Ultrasound uses high frequency sound waves to create an image inside your body. From this image, your doctor or technician measures the transparency, or open space, in the back of your child's neck.
They can then enter your age or date of birth into a computer program to calculate the risk of your child having an anomaly. NT scan cannot diagnose Down syndrome or any other chromosomal abnormality. The test only predicts risk. Talk to your doctor about available blood tests. They can also help assess the risk to your child.
As with any forecast, the degree of accuracy varies. If you combine an NT scan with a blood test, the screening is about 85 percent accurate in predicting the risk of Down syndrome. If you do not combine a blood test with a scan, the accuracy drops to 75 percent.
How to prepare for the test
NT scanning does not require special training. In most cases, testing is completed in about 30 minutes. During the scan, you will lie on the examination table while the technician passes the ultrasound probe over your abdomen.
Ultrasound images may be easier to read if you have a full bladder, so your doctor may recommend drinking water about an hour before your appointment.
The ultrasound technician needs access to the lower abdomen, so make sure you wear comfortable clothing that makes it accessible. Scan results may be available on the day of the test and your doctor can discuss them with you before you leave. It is important to remember that getting an abnormal NT scan result does not necessarily mean that your child has chromosome problems. Similarly, normal test results cannot guarantee that your baby will not be born with Down syndrome.
This test isn't perfect. There's a 5 percent false-positive rate. In other words, 5 percent of women tested receive positive results, but the baby is fine. After a positive result, your doctor may suggest another blood test called prenatal cell-free DNA screening. This test examines fetal DNA in your bloodstream to assess your baby’s risk for Down syndrome and other chromosome abnormalities.
Screening versus diagnostic testing
Getting inconclusive or positive NT scan results can be scary.
Keep in mind that an NT scan can only predict your child's risk: it does not give a definitive answer about chromosomal abnormalities. The NT scan is a screening test, not a diagnostic test. There are differences between screening and diagnostic testing. The purpose of a screening test is to identify risk factors for a particular disease or condition. Diagnostic testing, on the other hand, confirms the presence of a disease or condition.
How to Diagnose the Abnormality
To diagnose a chromosomal abnormality, ask your doctor about diagnostic testing. Options include amniocentesis, where a needle is inserted through the stomach into the amniotic sac to obtain a fluid sample. The amniotic fluid contains cells that provide genetic information about your baby.
Another option is chorionic villus sampling. A sample of your placental tissue is taken and tested for chromosomal abnormalities and genetic problems. With both tests, there is a small risk of miscarriage.
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