My AN was diagnosed when my 2nd was about 4 months old (I suddenly lost hearing halfway through the pregnancy, but no one would do any tests while I was pregnant). I know I had the AN during that pregnancy, and am fairly certain it was there for my first as well. It shouldn't affect the pregnancy, but do be careful about watching for changes in your balance. That was a big problem for me with #2 (before I knew the cause of the problem). When I hit the second trimester and starting to get some of the normal pregnancy swelling, my balance was completely shot. Between the swelling and vestibular changes and the regular pregnancy-induced center of gravity changes, I had to be extra careful to not hurt myself!
My doctors do believe, though there is not enough of a data pool to scientifically prove it, that the hormones related to pregnancy, breastfeeding, and menopause can cause ANs to grow faster than you'd otherwise expect them to, but won't cause an AN to grow that wasn't already there to begin with.
I had surgery when my second was 18 months, and then went on to have a third child earlier this year. My MRI this fall was perfectly clean, so that pregnancy didn't do anything AN-related. Yay!
Congratulations!Katie