It involves a blood test and measuring the fluid at the back of the babys neck (nuchal translucency) with an ultrasound scan. This is sometimes called a nuchal translucency scan. The nuchal translucency measurement can be taken during the dating scan.

What happens at your 12 week ultrasound appointment?

What Happens During the 12-Week Ultrasound? Your doctor will likely perform a transabdominal ultrasound, which transmits waves through your abdomen. In some cases, a transvaginal ultrasound may be performed to capture more direct or detailed images. A scan usually takes 20 to 30 minutes to complete.