Would removing the birthmark on my stomach result in a big scar? (Photo)

It would not! The best procedure for removing your birthmark would be to use laser treatments, like those used for removing tattoos. After a series of treatments, your birthmark should be removed without scarring, though hyperpigmentation and skin color variation may occur. Schedule a consultation with a dermatologist to get a formal evaluation. 

This can be removed with tattoo lasers. It will take a series of treatments. I recommend getting a formal evaluation with a cosmetic dermatologist. Best, Dr. Emer