Hgb 6.6 two days after delivery. Did not produce milk and had ppd. Could have these been prevented with a blood transfusion while in the hospital?

Unclear. A healthy woman, given iron should correct even a severe anemia in a few weeks if given iron. The decision to transfuse would be more related to the severity of the anemia symptoms. I cannot see how the anemia would be related to milk production. Re ppd, anemia could cause such fatigue that it might be hard to take care of the newborn, and that might contribute to ppd.