I have three children also, The first pregnancy was a disaster, it was very hard emotionally, but more so because of circumstance I think. Second was pretty good, mostly happy times, but not manic. Third was stressful but still good. I was in a very stressful marriage, so It's hard for me to tell whether it was the bipolar or the situation.
I went through all of my pregnancies, on no meds, and no pdoc, because I was still in denial over the whole thing. But it turned out pretty well. I did have post partum depression afterwards tho, and it was the worst after my third child. But at the same time my marriage was collapsing.
I have heard of a lot of bipolar women having great stable pregnancies, that more more stable then, than any other time. So I think it really depends.
Hope you keep posting!