bill go back 75 to 100 years and there weren't medical books either. Midwivery, and medicine, and law were learned from apprentiships. there weren't formal schools, and there weren't text books. even when the formal schools started (like the first medical and nursing schools) there was very little in the way of "class room" training, and 90% of the training was hands on, not read from a book. (there were lectures, but not text books!)

While the woman might have been somewhat literate, they certainly didn't have opportunites to go to formal schools (even Dr Blackwell had to fight the establishment to get into medical school..just what 100 years ago? )why would a midwife write a book? who would read it? there weren't schools for midwives. (or even schools for woman to be come Ob/Gyn's) let's not forget.. doors where closed to woman. show me the law books and the law school abraham lincoln went to or used? you can't. he read law, not text books, and he learned by working with an other lawyer as clerk. so too, women learned, by doing, and helping.
we know the iliad today, because for 1000 years before the greeks got to writing it down, it was passed on as oral knowledge. a lack of text books is not a lack of knowledge.