What Causes Persistent Bleeding After Medically Managed Miscarriage?

my partner had a medically managed miscarriage. had a little bleeding during week 12 and had a scan that confirmed of no heart rate. this was 5 weeks ago. bleeding has slowed considerably but still trickling for the last 10 days. phoned the hospital who have booked us in for next thursday. this afternoon, bleeding has increased a little and is now fresher (more red) blood. my partner is also "aware" of her lower stomach/womb area. any advice would be appreciated.