Why can the ultrasound for pregnancy travel through your body if a laser light or a flashlight cannot?

A ultrasound is exacty how it sounds. It sends out waves of sounds that bounces around your stomach and bumps into matter which then turns around and produces a picture for you. A laser light/flash light is used to light up space and is measured in sight not sound. If you stick a flashlight/laser light down a long dark tunnel it will only go so far as light can only be seen to a certain distance which is measured in how much power is produced. Yet, if you lets say put a light upto something that is not opaque and is hard to see thru as it is you won't be able to get the light to go thru the other side. Sound and Sight are completely different as you can see. (Disclaimer: I am not a scientist, this is just what I have accumulated in knowledge over the year"s".)