How does an ultrasound produce an image of a fetus in the mother’s uterus?

An ultrasound can produce the image of a fetus by using waves that are labeled as "ultrasound waves" or in ultrasonic frequency.

This may seem like an odd concept but you should note that everything we see and hear is made up of waves, like light and sound, that are at different frequencies.

The reason why there are different color lights are because there are different type of frequencies.  Some frequencies, such as ultrasonic, we can not see with our human eye.

Ithink its because more have died recently than in the past.

Yes yes yes very good