CONGRATULATIONS!!!!!! WHAT A CHRISTMAS PRESENT!
I, too, have heard of this happening a lot. The body is a strange thing isn't it? I had trouble conceiving my first (tried two years) to the point of needing fertility drugs. When I tried for baby #2, I got pregnant the first time I tried (no drugs, no anything). Maybe our bodies are more relaxed when we already have one *in the nest.* Oh this is so much fun and I am sooo happy for you!