I met my friend who is a o&G doctor in England, I, 8 abt your plb of 胎盤低 and the relation of bleeding. She mentioned that your case bleeding might not be related to 胎盤低, in yr case this is called uterus low lying, not exacting 胎盤低. She said no need to worry abt 胎盤低, as this is too early to said this and bleeding is no harm as long as you don't have pelvic pain. She suggested you to get a 3rd consultation which you did today.
Anyway, just some nossy stuff to share.
BTW, I already taking 4D scan as my doctor has that facilities too. But it will be more cost effective if you start from week 20 as using 4D, you can record DVD apart from picture.
mainly bb structure, backbone, counting the fingers, nosetrails, everytime the doctor will did both 3D and 4D together, so will update the bone structure for me too.