What is the first trimester nuchal translucency measurement?
Screening for fetal chromosomal abnormalities can include a sonographic measurement of fetal NT (the anechoic soft tissue posterior to the cervical spine or occipital bone) in the first trimester between a gestational age of 11 to 14 weeks. NT measurements are used in conjunction with maternal serum biochemistry to determine the risk of having a fetal chromosomal abnormality, most commonly Down syndrome. There are strict guidelines for measuring NT to ensure an accurate measurement of the sagittal nuchal thickness with the fetal neck in the neutral position ( Figure 58-3 ). A NT measurement greater than 3 mm from 11 to 14 weeks is considered abnormal.
