It is possible to calculate the nuchal translucency with an ultrasound done between the 11th and 13th week (up to 13 weeks and 6 days). During this ultrasound, the amount of fluid in the baby’s neck is measured to give the nuchal translucency. If this amount is larger than normal, there is a high risk of trisomy 21; such a measure can also indicate other risks of complications. We will also verify the presence of the nose bone, its absence indicating a higher risk of trisomy. This ultrasound can also be used to date the pregnancy.