Some good suggestions so far; I agree with Sean that a softbox would be a good modifier for this type of shot. The westcott Apollo series seems quite good and not too expensive (I personally have the apollo Orb which has the bonus of giving nicely shaped catchlights in the eyes). An apollo orb softbox was used for this shot (with an umbrella used for fill) and black fabric for the background. Separation from the background also helps to keep it full black, but if some light spills then you can darken it additionally in post if necessary.


Expecting by NFLD Stephen, on Flickr


Something else I noticed about the picture is that it seems to me like the lighting on her left hand does not match the lighting directly above on her belly. The light on the belly seems to be fading away, but the hand on that side still seems well lit. If you want both hands to be well lit like this you may need another flash to direct some light at the hand furthest from the light (perhaps with a snoot to keep the light from spilling on the belly and keeping that light fall-off). But maybe I'm just overcomplicating it...you may be able to just position her left hand a little more forward so it catches the light better.

Stephen