I didn't feel movement with this one (my third) until REALLY late - considerably after the 18 week mark. Scared me quite a bit, and I didn't have a MW or anything at that point. But there's definitely movement now! (37+ weeks) Probably NOT worth worrying, not for another few months at least - although I do remember wishing I had a doppler to cure the "what-ifs" (even though I'm against doppler use in general).
11/1/08 at 9:03pm