I feel it's a total personal thing. That said. I think it's a surprise no matter when you find out. For me, know up front kinda let's me think more about who they are rather than just "baby". I know gender has little to do with personality but with two girls already, my thinking was, "awesome! I know how to be a dad to girls, second I got this! Fancy dresses and cars and now and arrows and Legos!" First daughter was very girly. Second one wants to wrestle me, work with tools, ride bikes and her favorite color is blue. So go figure! But whatever you do, do right by you, or what your wife wants. :)