pelvic ultrasound is the usual ultrasound checking the amniotic fluid, placenta, gender, position, and AOG of baby. CAS is also a pelvic ultrasound pero mas detailed ang pagcheck kay baby. mas matagal itong ginagawa as compared sa pelvic ultrasound. checking baby's development and makita kung may congenital problem kay baby. tinitingnan each parts and organs ni baby, from head to toe, while in womb. my OB-sonologist explained everything to me while looking kay baby sa monitor.