Hi Fawcey,
I am tempted to suggest that
anything that requires women to climb to 6000 ft will reduce their chances of getting pregnant, unless they take male companionship with them of course.
Maybe the New Guinea version of "Sorry dear, I have a headache," is "Sorry dear, I have to climb to 6000 ft and eat a mushroom..."?
To attempt to be more helpful, I have looked in a few books and not found anything I am afraid.
The mention of maitake may be a bit of a red herring. True a Google search will bring up mentions of maitake, but it is important to examine the context . There are too many references to wade through, but my impression is that while maitake is often mentioned on webpages that also mention contraceptives, these are general medical (or pseudo-medical) pages covering a number of topics on the same page (and often attempting to sell potions of one sort or another). A lot of the web pages are of the type that we warn our own students against uncritically accepting.
Maitake does appear to have properties of use in treating tumours, excess blood protein and maybe high blood pressure, so it might well be relevant to your assignment. A possibly useful weblink is:
http://www.cancer-articles.com/canc...tate-cancer/prostate-cancer-article-2775.html
Maitake is
Grifola frondosa, a bracket fungus that grows on beech (Fagus) and other trees and which seems to occur worldwide. Here in the UK I have regularly been driving past a fine colony where a beech has been felled. (Not seen anyone trying to eat it though.)
Coming back to your original question - I wonder how reliable the original information is? It might well be hearsay - a vague story that the author has heard and decided to use but has no foundation in fact anyway?