This is the first scan that is advised in a pregnancy. 

a) This scan helps to find the date (confirm or calculate expected date of delivery). 
b) Assess the baby's growth up to this point. 
c) Single baby or twins or more. 

During the scan we can see the fetal head, spine, limbs, stomach and fetal heart activity. Seeing the major organs of the baby assures us that things are normal. Sometimes, to see the baby better; an internal (vaginal) scan may be needed.

Nuchal translucency (NT)

A small amount if fluid seen behind the neck of all babies. The measurement of thickness of the NT is recommended during this scan. This by itself, or in combination with a blood test, helps in predicting the risk for Down Syndrome (DS).

Some may choose, the alternative MyNIFTY test which requires only maternal blood for DS screening.

Twins : This scan allows to identify, if they share the same placenta or have separate placenta. Twins sharing the same placenta need close monitoring and this scan will help to obstetrician in planning the future course of management.