What is the Catholic stance against In Vitro Fertilization?

I was researching a different question and saw that some people find that In Vitro Fertilization (IVF) is something that should be avoided on the basis of religious grounds. Does anyone know what these reasons are? I'd like to know if these religious arguments against IVF are biblically based. If so, what passages do they use to support this argument? (This seems especially strange to me since pregnancy wasn't fully understood back then, let alone IVF.) Specifically, I would like the Catholic stance on this.