I am pregnant. Is it bad to be around a child who is diagnosed with scarlet fever?

Scarlet... ...Fever is just a strep throat that runs with a rash. A child with this disease would be contagious for about 24 hours after the first dose of antibiotic, and is safe after that.
Stay away. This is a potentially transmissible disease and best remove yourself from contact with the child until treated. Once on antibiotics there should be minimal risk of transmission to you.