Growth scans how oftern ?

Michelle • 33 year old from Australia , currently pregnant with baby #4 a boy..miss 7 mr 5 miss 1 and prince due 26/01/17
So I had my monthly checkup with midwife today , and have been told I'm needing growth scans done at 28 weeks 32 and 36 weeks , . Is it normal to have this many scans ? I'm currently 20+4