Hi, I had an u/s at 12 weeks because the midwife thought I seemed big and we needed to check if there were twins. Turned out to be only one baby, but during the u/s they noticed the placenta was lying low, right next to the cervix. In one of the birth articles about u/s on the Mothering website it talks about 95% of low lying placentas detected in early pregnancy move up into the proper position. In another article that I read on a website called MedScape, it said that the later in a pregnancy that a low lying placenta is detected, the less likely it is to move up. Because mine was detected so early, I have opted to not have another u/s unless the midwife feels it is really necessary. So far she hasn't mentioned it again and I'm at 34 weeks now. She told me, after we got the results of the first u/s, that it was not something to be very worried about, that it was common in early u/s, and that if the placenta did not move up, we would definately know because there would be bleeding around the time of labor or near the end of the pregnancy. This is how it is detected in a person that has not had any u/s. So, that's where I am at. Since you mention that you had bleeding from your first birth, that might affect things differently for you. I don't know. I would ask your midwife if she feels what happened to you before could also affect the placenta now. That might be a good reason to have the u/s if there are other factors, such as scarring, that could prevent the placenta from moving. Good luck!! Praying your placenta moves up, up, up!!