Yes, waxing is safe while you're expecting. In fact, it's a much better option than using a depilatory cream, which is usually lye-based and needs to be left on the skin for a while. While no studies have ever linked depilatory creams to birth defects, it's best to play it safe and wax or shave instead.
Just remember that increased blood flow to the skin during pregnancy -- especially down there -- could make bikini waxes a bit more painful now than ones you've had prior to expecting. You're also more likely to experience broken blood vessels and ingrown hairs (harmless, but unsightly). Don't say we didn't warn you!