What Happens to First Trimester Nuchal Translucency

First trimester nuchal translucency is a call point for genetic abnormalities and birth defects. Nuchal translucency varies with LCC and therefore with gestational age as described by Chung et al who created a 99th percentile curve of nuchal translucency versus LCC. The majority of centers use the 3.5 mm cutoff as the 99th percentile instead of using nuchal translucency based on LCC. The objective of this study is to compare the fate of nuchal hyperclites> = 99th p but <3.5mm versus 3.5mm. For this the investigators have studied the ultrasound and genetic abnormalities. The investigators were also interested in the pregnancy outcomes and the percentage of pregnancies in the group> = 99th p and <3.5mm that would have been sampled for a high combined risk for trisomy 21, and therefore to determine the benefit of a systematic sample. for HCN as well as the interest of performing an ACPA that would not be performed on a sample with a high risk of trisomy 21.