be careful, after spray tans start to fade, you don't look tan anymore. you look orange lol. i prefer to be a whitey if i can't tan. rather look normal than like an oompa loompa lol
It's safe, and no the color will not come out different. You can double check with your doctor regarding safety for baby.
The only other thing I can think of is that a women's skin becomes more sensitive during pregnancy and so you might become itchy, etc, from something in the spray/lotion, but you might not.