With baby # 1 I had quite a sustained bit of spotting. I was told by the ob that so long as it was brown/dark brown there was nothing much to worry about - it was 'old blood' and that sometimes bleeding can occur when the placenta buries into the uterus wall it can hit a blood vessel. He said that it was quite common and not to worry. When you may get concerned is if you get bringht red blood. I am currently experiencing some really light spotting this time too - earlier than I had last time, and seeing as I haven't had a bt yet and its VERY early days, I'm trying o take my own advice and not panic. all the best and good luck!