asking for ultrasoung

hi mga mamsh, ask ko lang ilang ultrasound po ba dapat? as per my ob ok nman po lahat nang ulrasound and result nang lab ko,naka tatlong ultrasound na po ako and im 28weeks pregnant now, then required ulit more 3 bps ultrasound daw. thanks po sa sasagot. 1.pelvic 2.cas 3.bps