When is a neck wrinkle measurement performed?
Neck wrinkle measurement is usually performed as part of first trimester screening between the 11th and 14th week of pregnancy. During this period, a thin fluid seam forms in the baby’s neck, which can be seen as a bright spot in the ultrasound scan. As the organs mature during pregnancy, the accumulation of fluid in the neck disappears again.
In the ultrasound one would then see no or only a very minimal “neck fold”. Statements of an examination after the 14th week of pregnancy would therefore not be meaningful. A neck wrinkle measurement should also not be carried out before the 10th week of pregnancy, as the baby is still too small at this time and the values could be falsified.
The best time for a neck wrinkle measurement would therefore be around the 12th week of pregnancy. The time window between the 11th and 14th week of pregnancy is suitable for the measurement. Before this time the fetus is too small and the results cannot be evaluated. Later, the fluid is broken down by the increasingly better functioning kidneys and the better developed lymphatic system of the child, until at some point it is no longer visible in the ultrasound.
What does the measurement say?
Normally, the thickness of water accumulation in the nuchal fold in the healthy fetus is 1mm to 2.5mm. Starting at 3 mm, one speaks of increased values, starting at 6 mm of strongly increased values. If abnormal results are measured during the examination, it is not yet possible to make a final diagnosis about certain malformations.
One can only determine the probability of a malformation by the extent of water accumulation. A change in the nuchal fold occurs in the context of various developmental disorders such as Down syndrome, Edwards syndrome (trisomy 18) or also in heart defects. It is not uncommon for children with abnormal neck wrinkle thickness to be born completely healthy and without any developmental changes!
For this reason, in case of abnormal findings, one should never immediately assume that a child will be born with a severe disability, even though most women immediately fear the worst. In most cases, the blood of the pregnant woman is also examined, because the blood test and the ultrasound result together give more precise indications of a possible malformation. This so-called triple test then measures various parameters such as the pregnancy hormone B-HCG.
Like the ultrasound examination, however, the measured values also only allow a purely statistical statement about the probability of malformation at a certain neck wrinkle thickness. Nevertheless, it is used frequently and with great reliability, because only by measuring the neck wrinkles alone can 80% of children with trisomy 21 be successfully diagnosed at this stage. By combining neck wrinkle measurement with the above-mentioned blood test, this probability can be increased to up to 90%.
Conversely, it is also important to note that 20% of all children born with trisomy 21 had an inconspicuous neck wrinkle at the time of the examination. However, further examinations are necessary for every suspected case. An amniocentesis, an examination of the umbilical cord, and a chromosomal examination can then provide final clarity.
Chromosomal analysis involves obtaining and examining cells from the unborn child by one of the above mentioned types of examination. However, these examinations are no longer as low-risk as the simple ultrasound examination, and the risk of infection for mother and child is increased by the amniocentesis.If a malformation is actually diagnosed, it is important to provide parents with support and assistance in order to be able to adequately accompany a possible abortion or the preparation for a life with a handicapped child. Parents must then be informed about alternatives such as surgery on the unborn child, adoption or an abortion and the consequences.
No matter what decision the parents make, they should be provided with the appropriate support. If a heart defect is diagnosed through the clarification, the latest advances in medicine should always be pointed out. For example, heart defects are still the death sentence for a newborn in the minds of many people.
On the contrary, in most cases they are operable with high success rates and thus almost curable. Heart defects can often be performed without a blood sample or amniotic fluid being taken, and a 3D ultrasound or a so-called Doppler examination can be meaningful enough. The Doppler examination is also performed as part of an ultrasound examination and uses ultrasound waves to measure the blood flow in the vessels of the unborn baby using the same principle as above.
This allows most heart defects to be assessed or excluded. The neck wrinkle measurement is carried out with the help of high-resolution ultrasound devices, which have the ability to measure the density of the neck wrinkle. These values are usually related to the size of the unborn child (crown-rump length) and the age of the mother and then compared with reference values.
For example, neck wrinkle values above 2.1 mm in a 45 mm large child are suspected of trisomy. In children 85mm tall, the thickness should not exceed 2.7mm. Higher values would also indicate a malformation of the child.
If, in addition to the conspicuous measured values, an increased age of the mother (more than 35 years) is added, the probability of a possible malformation of the child is high. Ultimately, however, it must be said that the neck wrinkle measurement alone is not sufficient for a diagnosis. Even healthy children can have thickened neck wrinkles without any malformation.
These would be mistakenly diagnosed as sick by a neck wrinkle measurement although they are actually healthy. Studies have shown this – 6 out of 100 children were diagnosed as sick even though they were healthy. With the help of further examinations (e.g. amniocentesis (amniocentesis) or chorionic villus sampling) this misunderstanding can finally be clarified.
This is to show that a neck wrinkle measurement, although very reliable per se, can also provide misinterpretations. For this reason, it should rather be regarded as a probability determination than a final diagnostic possibility. However, since it provides a high degree of certainty as to the diagnosis of a malformation and, in comparison to other examinations (such as amniocentesis and chorionic villus sampling), does not pose any risks for mother and child, neck wrinkle measurement as a screening method is a means of first choice. Heart malformations and metabolic diseases can also be reliably detected by it.
