There are many books on pregnancy and birthing out there, but I recommend only a few. Too much reading (especially about what could go wrong) was not good for me while expecting (do it after or before, but not during). The books I recommend all have to do with a little bit different approach to pregnancy and child-birth. While most conventional books will say that you should not use any herbal teas, some of them will offer extensive information (which I have used) on what plants and how to use during pregnancy.
karinadoula 