Hi Lisa
A subchorionic bleed is a bleed between your placenta and the wall of your uterus. A small bleed is usually not a problem and the blood will often be reabsorbed by your body. If this happens then the placenta may well also reattach where the bleed is. If the placenta does not reattach at this point then as the area is only small it should not cause you any worries. However I would expect your doctor to want to keep an eye on it.