What to do if » Increased nuchal translucency
When the thickness of the fluid in the back of the fetus’s neck is increased (increased nuchal translucency), a qualified practitioner can help the patient in choosing the best way to manage her pregnancy
The measurement of nuchal translucency will vary depending on the gestational age.
Generally it is said that the thickness is increased when it is above 2.5 mm. However this is valid only when the measurement is taken when the size of the fetus is 45-60mm, while it is considered to be normal if measurement is taken when the fetus is more than 70mm long.
There are many reasons why the nuchal translucency is increased.
The incease of NT is associated with:
Once it has been confirmed that the NT measurement is increased (assuming that the measurement is conducted by following the criteria described in this website), the main objective lies in differentiating fetuses with chromosomal or structural anomalies, from those that are likely to have normal development.
As illustrated in the table, there is a positive correlation between an increased nuchal translucency and risk for chromosomal defects or other pathologies
:defined as less than 2.5 mm
:between 2.5- 2 3.4 mm
A POSITIVE test result does not imply that the fetus has an abnormality but it is advised to have further investigation.
A positive risk for T21 or other trisomies is when the risk is higher than 1/100. Therefore a risk of 1/90 is positive and 1/110 is negative.
Before concluding that the test is positive, it is important to take into account other markers such as
The practitioner should help the patient understand the reasons or factors in the test that have contributed to an increased risk:
Both nuchal translucency and blood test contributed to a positive test:
In this case, with both increased nuchal translucency measurement and positive blood results, it is more likely that the fetus has a chromosomal abnormality. In cases of structural anomalies, blood results will not vary.
PROCEDURE TO BE FOLLOWED WHEN A TEST IS POSITIVE
The diagram a practitioner should follow with high risk pregnancies is as follows:
*From 2013 in case of result that suggest intermediate or high risk a non invasive test can be offered (Harmony prenatal test™)
If no fetal defects have been identified the parents should be reassured of the fact that the fetus has good prospect of being born and develop normally.
In these cases, the risk of malformation or problems of neurological development, should be comparable to that of the general population.
In cases where there is a family history of genetic syndromes
If at 14-16 weeks the measurement of NT remains high but there are no evident fetal anomalies or there is an indication of an evolution towards a nuchal edema or fetay hydropes at 20-22 weeks, the possibility of a congenital infection or genetic syndrome must be considered.