First trimester screening
First trimester screening is performed between 11 and 14 weeks of fetal development of unborn babies. The doctor pays special attention to the so-called neck area, the size of which is determined by the amount of accumulated lymphatic fluid in the occipital region of the fetus. The increase in number could signal the presence of a possible genetic defect such as trisomy 21, which is the cause of down syndrome.
The dimensions of the neck area
The size of the neck area depends on the age of the fetus. At the beginning of the 11th week of the normal value of up to 2 mm by the end of the 13th week it can reach 2.8 mm. it is not necessary to panic if the numbers are slightly inflated. According to statistics, 9 out of 10 children with the size of the neck area between 2.5 and 3.5 mm are born perfectly healthy. And only when the index is significantly overvalued, such as 5-6 mm or more, it is possible to suspect the presence of a genetic defect. After 13-weeks formed the lymphatic system of the fetus, the fluid from the neck area spreads through the vessels of the body, and the measurements cease to be relevant.
Moreover, it should be understood that these figures though are considered quite important in prenatal diagnosis, in and of themselves are not a diagnosis. It's just a screening that helps to assess the risk of occurrence of a disease. Therefore no doctor has the right, based only on the high value of the size of the neck area, to send a woman to an abortion. Accumulation of lymphatic fluid in the neck does not necessarily mean that the child has some genetic defect. On the other hand, no one can guarantee that the fetus with a normal neck area could be born perfectly healthy. Therefore, as may be necessary and other studies. For example, cordocentesis or analysis of amniotic fluid, which can provide more specific data about the health of the baby.
Besides do not forget about the likelihood of measurement error. The fetus is still so small and measure down to tenths of a millimeter is difficult. And the unit may be old and the doctor still not so experienced, and the position of the fetus not the best, so if the first trimester screening were obtained questionable results should always double check with another professional, and other equipment.