While some people wait until their baby is born to find out their biological sex, others want to know as soon as possible.

You may have heard that a faster fetal heart rate indicates a girl, while a slower one might mean you're having a boy — but is there any truth to this theory?

A diagnostic medical sonographer could be answering the question "Is it a boy or a girl?" as well as a host of other life-changing medical questions with the help of ultrasound technology.