I had the opposite problem... excess fluid. But, reading up on that I've come across lots of good info on low fluid too. First thing, if it was a serious case of low fluid, they would have made that very clear to you, so I wouldn't get all worked up about baby running out of fluid just yet. Like the pp said, drink lots of water! Your fluid level depends on it and you can have it up long before your next u/s. Also, you can soak in the tub and that supposedly helps. Just be sure the water isn't too hot. More than likely, if it wasn't a serious case of low fluids, they just caught it at a bad time and it'll all be fine at the next one.