Transvaginal ultrasound in the first trimester of pregnancy has an important role in the estimation of the risk of chromosomal alterations.
Commonly dating scans (or booking scans) from 7 weeks confirm pregnancy dates and look for twins.
At 11-13 weeks the ultrasound detection identify some parameters such as the length craniocaudal (LCC) of the embryo, the nuchal translucency (NT), the presence of the foetal nasalbone and the ductus venosus. The first trimester ultrasound must also include the study of the basic morphology of the head, trunk and limbs of the embryo.
