Those superstitions make me really angry. Buying or having baby stuff will not magically cause a miscarriage or stillbirth, there are biological reasons for those. All the superstitions do is increase the pain of a loss by blaming the parents (often the mother who is already suffering both emotionally and physically) for getting to excited about the arrival of their child. Screw that! A pregnancy is an exciting time, worth celebrating and feeling happy about. If someone wants to wait because having stuff would be too painful after a possible loss, then by all means wait. But I hate it when other people try to make expectant parents feel bad for wanting to be optimistic and confident about their pregnancy.
/rant