Although it can be done a little before or a little later, today the most common time to make a first trimester ultrasound It's 12 weeks. This is because at this time the anatomical development and the size of the fetus make it possible to verify that most organs have been properly formed. A high-level ultrasound at this time can detect up to 60-70% of the possible malformative problems that will appear during pregnancy. The other measurement that is made is nuchal translucency, the fluid that all fetuses have in the neck.
Biochemical screening
Screening allows estimating the risk of having an anomaly in the number of chromosomes (technically defined as aneuploidies), especially the trisomy of par 21 or Down syndrome.
In 1866 Langdon Down He noted as common characteristics of patients with trisomy 21 the deficit of elasticity in the skin, giving the appearance of being excessive for the body, and the face flattened with the small nose. In the ninetiesIt was described how the excess skin of individuals with Down syndrome could be visualized by ultrasound as an increase in nuchal translucency in the third month of intrauterine life.
For the risk calculation, the value of nuchal translucency, with mother's age, and the values of two hormones (beta-HCG and PAPP-A) that have been performed in blood analytics they place the anomaly detection rate around 95%.
In addition to its role in calculating the risk of trisomy 21, the increase in nuchal translucency can also identify a high percentage of other chromosomal abnormalities, and is associated with major abnormalities of the heart and large vessels and to a broad spectrum of genetic syndromes.
Other advantages of the first trimester ultrasound
The confirmation of fetal viability, the precise calculation of gestational age, the early diagnosis of major abnormalities in the fetus, and the detection of multiple pregnancies. Early ultrasound also provides the possibility of reliably identifying chorionicity, the main determinant of perinatal outcomes in multiple pregnancies.
The calculation of the risk of preeclampsia. At the moment it is an option that can be done in very few centers and is not offered in a generalized way.
As you can imagine from all the above, it is very important that you perform this First trimester ultrasound.
