We happened to see a TV programme called "William and Mary" the other evening. Mary is a midwife, and after the thing had finished my best-beloved reached for the dictionary and then finally today I looked it up in the AHD for a bit more info' which I thought I'd share:

ETYMOLOGY: Middle English midwif : probably mid, with (from Old English; see me-2 in Appendix I) + wif, woman (from Old English wf).

WORD HISTORY: The word midwife is the sort of word whose etymology seems perfectly clear until one tries to figure it out. Wife would seem to refer to the woman giving birth, who is usually a wife, but mid ? A knowledge of older senses of words helps us with this puzzle. Wife in its earlier history meant “woman,” as it still did when the compound midwife was formed in Middle English (first recorded around 1300). Mid is probably a preposition, meaning “together with.” Thus a midwife was literally a “with woman” or “a woman who assists other women in childbirth.” Even though obstetrics has been rather resistant to midwifery until fairly recently, the etymology of obstetric is rather similar, going back to the Latin word obstetrx, “a midwife,” from the verb obstre, “to stand in front of,” and the feminine suffix –trx; the obstetrx would thus literally stand in front of the baby.

Ed: Sorry, I guess I should have put this below the line in "Words from Medicine".