Not sure - as they looked at the placenta and couldn't see any issue. So could have been something else (and I can't remember exactly what a Subchorionic hemorrhage is....placenta (chorion) related...).
Bleed at 26wks, that landed me in hospital for two nights, some steroids, an internal (not comfy at all), and monitoring. C-section at 39wks (due to positioning) of a healthy 6lb13oz girl.
May have been a twin pregnancy where one was a blighted ovum (implants, creates a wee placenta, but no baby, usually ends in early miscarriage), and the other was our daughter - no miscarriage in early pregnancy due to the actual baby - but she got pushy at 26wks and 'kicked out' the placenta looking thing is our theory.
So I could be on the completely wrong page with this answer (as bubs placenta was fine). Just wanted to share a good outcome if I was on the right page!