What is a nuchal translucency measurement?
When measuring nuchal translucency, your doctor uses ultrasound to measure the lymph fluid under the neck skin of your unborn baby. With this exam, your doctor will get an indication as to whether or not there may be any specific chromosis. An enlarged neck fold is larger than usual, which may be an indication of trisomy 21 (Down syndrome), for example.
However, this test is not a diagnosis. It is a so-called screening that only assesses a risk for a specific chromosome. A large neck fold does not necessarily mean that such a feature is present in your baby. On the other hand, the neck fold may look normal and yet everything is not all right. Your doctor must clarify this with additional or subsequent diagnostic tests.
When can I have a nuchal translucency measurement done?
The nuchal translucency measurement is usually done between SSW 11 and SSW 14. Before, the measurement is difficult because your baby is still too small and therefore the results are inaccurate.
After pregnancy week 14, the lymph fluid under the neck skin less so because your baby's lymphatic system continues to develop.
How is the screening done?
The main part of the test is an ultrasound examination. Usually an ultrasound is enough over the abdominal wall. But sometimes your doctor needs a better look because your baby is not properly seen. Then your doctor will do a vaginal ultrasound scan. This is completely safe for you and your child.
Your doctor will determine the breadth of nuchal translucency. You can follow this on the ultrasound scan: your baby's skin appears white, the fluid under the skin looks black. Maybe you will not recognize everything, but still that's exciting for you because you see your baby! On this ultrasound, your baby will fit in the picture: you will be able to see his head, spine, arms, legs, hands and feet.
Along with the nuchal translucency measurement, your doctor will measure your child from the head to the lower end of the spine to see how tall your baby is now. This will help your doctor to better figure out in which pregnancy week you are.
How reliable is the nuchal translucency measurement?
In a large study, 100,000 pregnant women were examined with a nuchal translucency measurement. The researchers found 75 percent of all cases of babies with Down syndrome out. In addition, if a blood test is made, the enlightenment rate rises to about 90 percent.
Crucially, nuchal translucency measurement is performed carefully and accurately, and therefore strict standards apply to this screening. The doctor must be certified by the Fetal Medicine Foundation to perform the test and to use the risk calculation database. This certificate must be renewed annually by the doctor.
It is also important that the ultrasound device has a sufficiently high resolution.
Where can I get the nuchal translucency measurement done?
Because of the above-mentioned doctor's certification, only a few gynecologists will offer you the option of a nuchal translucency measurement.
The nuchal translucency measurement, in which a blood test is done at the same time, is called first trimester screening. With the combination of ultrasound and blood test, doctors can estimate the risk fairly accurately.
Here you will find doctors who have the right to carry out the first-trimester screening: fmf.deutschland.info
The gynecologist will advise you thoroughly before the examination. Above all, it is about how you want to deal with the result if the measurement results in a risk.
What are normal values for a nuchal translucency measurement?
The value of nuchal translucency (NT value) increases with the baby. It is therefore larger in later weeks of pregnancy than in earlier ones. In general, values between 1.0 and 2.5 mm are considered normal.
1. Normal nuchal translucency
On the left picture see a baby with a normal NT of 1.3 mm. There is little risk for this baby. The picture right shows a baby with an NT of 2.9 mm, just above the upper limit. But nine out of ten babies with NTs between 2.5 and 3.5 mm are completely healthy.
3. Great deviation of nuchal translucency
The NT on the Picture left is very rare. The nuchal translucency of the baby is 6 mm. The risk of this baby having a specific chromosome or an organ defect is significantly increased.
When do I get the results of the screening and what's next?
You and your doctor see your baby together on the ultrasound. Your doctor will do the measurements and then he / she can tell you what they mean.
You may want to take your partner or a good friend with you for the examination. On the one hand, you can then look forward to the ultrasound together. On the other hand, you have someone with you when you get the results. Even if the nuchal translucency measurement is not a diagnosis, but only an indication of a risk, it can disturb you, if everything does not seem to be all right.
Your doctor can already detect a major problem such as a serious malformation. Nevertheless, he / she will offer you another ultrasound scan between weeks 19 and 22. In this so-called organ screening you can see a lot more, because the baby has grown again quite a bit.
Should the nuchal translucency measurement be conspicuous, your doctor will recommend you diagnostic tests to be on the safe side. Chorionic villus sampling (CVS) and amniocentesis (amniocentesis) are such tests. Both provide a clear diagnosis, but both have a very low risk of causing a miscarriage. That's why you do not do these tests until the nuchal translucency measurement or first trimester screening is a concern. After the nuchal translucency measurement, you can still decide if you want to know more.
How can I interpret the results?
Your doctor will explain the results to you. If you do not understand the explanation, just ask.
Here are a few pointers for you to better assess the risk:
- A low risk if you have the risk less than a woman of 300 is (1: 300). For example, if you read 1: 800 on the printout, it means that out of 800 women who have this risk factor, a woman is having a baby with Down syndrome.
- A higher risk if you have the risk higher than a woman of 300 is. A score of 1: 150 means that out of 150 women who have this risk factor, a woman is having a baby with Down syndrome.
What should I do if I have a high risk?
In about one in every 20 women the risk factor is high - but most of these women still get a healthy baby. Even if the risk factor is 1 out of 5, that still means that four out of every five babies are born healthy.
For you, a high risk factor means first of all that your doctor considers your pregnancy to be a high-risk pregnancy and that you will examine it more carefully and frequently during the remaining weeks of your pregnancy.
Of course it will make you nervous and you will be unsure how to proceed. Knowing whether your child is suffering from trisomy 21 or any other chromosomal change can only give you a CVS or an amniocentesis (amniocentesis).It may not be easy for you to decide if you want to take these tests. But you also do not have to break it over the knee: One benefit of nuchal translucency measurement is that you have the exam early in pregnancy and then there is plenty of time to decide on CVS or amniocentesis.
Be advised in detail by your gynecologist.