Nucal Translucency Bi Test

Nuchal translucency

It is an ultrasound examination which consists of measuring, between the 11th and 13th week, of a space located in the posterior region of the fetal neck. In this location there is a thin layer of liquid which is present in the nuchal region of all fetuses and which appears on ultrasound examination as a thin liquid area called translucency.

When this fluid layer is increased (increased thickness of the nuchal translucency) there may be an increased risk of fetal chromosomal or other pathologies, for example malformative heart disease. It can be estimated that the nuchal translucency study has a sensitivity of 75-80%. This means that 75-80% of fetuses affected by trisomy 21, or Down syndrome, can be identified by studying nuchal translucency.

BI-Test 

It is a blood test that is performed between the 11th and 14th week and is based on the dosage of two hormones (hence the name bi-test) present in the maternal bloodstream: the free-beta HCG (free fraction of chorionic gonadotropin ) and PAPP-A (plasma protein A associated with pregnancy). Free-beta HCG is generally elevated in the case of fetal chromosomal diseases. On the contrary, PAPP-A is decreased. So the more PAPP-A decreases and the more free-betaHCG increases, the more the possibility of chromosomal diseases increases, including Down Syndrome and Trisomy 18.

BI-Test and Nuchal Translucency (combined test)

The association of the BI-Test with the ultrasound measurement of nuchal translucency increases the sensitivity of the test for Down Syndrome to 90% (that is, it is able to identify 90 fetuses out of 100 with Down syndrome).

For more information www.fetalmedicine.com