The medical literature is not our friend in this. When I was
researching the chapter on 3rd stage for the new edition of Ob
Myths (book is now 2/3 written), I found two studies looking at the
relationship of 3rd stage duration and hemorrhage. Both
studies found that it was not linear. There was a spike in
hemorrhage incidence at about 30 min. The authors concluded that
this was the safe limit for waiting. But if you think about
it, you will see that extraction at whatever point in time would
precipitate hemorrhage either as a consequence of the underlying
reason why the placenta hadn't delivered, i.e. abnormally adherent
placenta, or consequent to the procedure itself. The apparent
threshold merely represents how long the typical practitioner was
willing to wait before trying manual extraction. I think what
does make sense, though, is don't try to get a stubborn
placenta out at home. You want to be in an environment prepared to
deal with it if all hell breaks loose along with the
placenta.
-- Henci