You can use these terms to help a child feel more safe and loved while visiting the clinic. You don't have to know them to use these terms. It is like calling a child kiddo, sweetie, or honey. Practice on your own children or loved one. It feels nice to be nice.
For girls, here are some...
For either a boy or girl...
Hola mi...amor, cielo...corazon
For boys, here are some...