I am trying to remember this same thing for myself. My first one weaned when he was 2.5 yo and I was 6 months pregnant with #2. I am guessing that my supply had dropped and he began to lose interest, however, it may have also been his age. Hard to know. I do remember that nursing hurt A LOT during the first trimester and then got easier again one I was into the second tri. Now I am pregnant with #3 and my DD is just 16 months old and still nurses quite a bit. So far, no changes that I can notice (yet I am just about 5 weeks), and I plan on nursing her as long as she wants...tandem nursing as well if need be. So I am curious to hear what others have to say!