I have had mate tea while on a medical mission trip to Bolivia last year. It
is a very common drink there and is made from coca leaves. Yes, the same
ones that produce a very popular street drug. Many Bolivians drink it all
the time and it supposedly cures all kinds of ailments, including altitude
sickness (though it didn't stop me from fainting away). Anyway, I don't
know if it has caffeine in it or not (seemed quite weak to me) or the
effects on preg. & lact. I do know that in the area we went to most of the
babies were bf. (the malnutrition came after they were weaned).