Hi Craig, there are many ways to acheive what you are looking for, its all about your model being considerably lighter than your background, this can be done easy with flash by just bumping up your power on your flash and directing it so it does not spill onto the background.
For babies I think natural light is the best for a softer look and using a narrow depth of field so that the eyes are in perfect focus and the skin becomes softer. Take a look at this video it may help you to see what can be done with natural light in a basic location.
http://www.youtube.com/watch?v=bbKa3...eature=related