Bleeding

Patient: Hi i am 12 weeks 1 day pregnant and tonight i woke to lots and lots of vaginal bleeding. also i have passed 3 hand sized clots. No pain at all and this the second time this has happened. last time it happened the ERE said i was having a miscarriage but when i had a scan they said the baby was fine. what could be the cause to this bleeding again

Symptoms: No symptoms

Doctor: