Preparation:  If your pregnancy stage is within the 1st trimester (0 to13 weeks), you will need a full bladder for the procedure. You must drink between 4-6 cups of water, half an hour prior to the exam, and don’t empty your bladder until the end of the examination.

The Ultrasound Markers are only possible between 12 to 13,4 weeks of pregnancy. 

The following variables are used (if applicable) as Ultrasound Markers: NT, NB, DV.