Skin Tone vs. Background?

[scorpion_tyr]

So I just set up my home studio, and did a maternity shoot that turned out really well. I used a black background and the couple I shot was white. (This is NOT a racist post!). Well the guy who sits right next to me at work saw the pics as I was showing them to another coworker and instantly booked me to shoot his pregnant wife this sunday. I've shot many different people of all different races, but I just started using backdrops and my little home studio, so here's my question:

For a black couple with pretty dark skin tone, would a white background work best, or maybe gray, or what?