Newborn Photography. So how small are these babies that you want/need the 100mm macro?
While this lens is spectacular... unless you're wanting super close up of toes/fingers, you might be better served with another lens. I find 100mm quite a bit "long" for indoor, and assuming your newborn photography will take you into many homes of your clients to shoot their little blessings, you might find the focal length too tight for framing. That's just my opinion anyway.
Im mainly buying this for Wedding ring shots + closeup of insects etc. (in my spare time). For newborn photography you're better of getting a portrait lens instead of macro lens.