Heavy Bleeding in Early Pregnancy: 12 Weeks & Ultrasound Results

Question
I'm 31, 6th pregnancy, 2 children.  LMP was miscarriage on 7 Aug 2005.  At 11w, I had an u/s that showed heart, limb movement.  10 days later, at 12w4d, I gushed blood, and went on to lose about 200cc in the ER.  Ultrasound showed 167 heartbeat, baby waving and moving.  OB second opinion saw no dark patches (bleeds) or anything concerning when he did u/s.  Sent home with progesterone on the off chance it might help.  Bleeding has tapered significantly overnight.  Any clue what might have happened?  The docs threw up their hands and said "waiting game" -- cause *that* makes a patient feel great... :)  Could a SCH have hid from everyone?

Answer
If you are bleeding, and the fetus has a good fetal heartbeat and there is no evidence of placenta previa or abruption, it may be a "subchorionic" bleed that was missed on sonogram. A subchrionic bleed is a sequestration of blood within the folds of the developing placenta. It normally occurs at around 11-12 weeks gestation as the placenta is being developed. This bleeding usually does not interfere with the pregnancy and will stop eventually. I can think of no other cause for the bleeding, unless a vessel in the vagina ruptured, causing bleeding.  You will have to wait and see.