I too really wonder about a mom who doesn't want to wait for the placenta to come naturally?! Will she wait to go into labor naturally? Why is she in such a hurry to get the placenta out? Has she had some bad 3rd stage problems leading to this fear?
I thought getting baby to nurse was the fastest, easiest, and by golly, most natural way to get the placenta out, no?
Other alternatives to waiting, nursing or injection, is a squirt of either Angelica or Motherwort tc, SL to hasten the plaenta. And worst case scenario, pit could be given IV in the anticub. if indeed she really needed it and the muscles were to mushy to inject IM. In any case, I wouldn't let the fact an IM injection may, or may not be possible scare me out of a waterbirth, if that's what I wanted to do.