As the other girls have said, it is usually just the two scans. Sometimes there is a need for a further scan if the Doctor is concerned about growth of bubs.

In my situation with carrying twins, I have already had a scan at 7 weeks to check for viability, another scan at 13 weeks for the nuchal testing. I will be having another scan at 20 weeks, then 28 weeks and finally at 34 weeks.

The last 2 scans are to check for growth of the babies