That's a LOADED question. Every plan is different (even within Humana). It might be best if your midwife called to verify benefits. She will know the right questions to ask.
Is your midwife "attached" to a free-standing birth center, OB/GYN office, or hospital? This may make a difference as well. You are entitled to coverage by a practitioner "working" at a covered facility even if the particular practitioner is not contracted.
In addition, if your policy entitles you to birth with a CNM or Freestanding BirthCenter but there is not a contracted provider within a certain distance (usually 50miles), then you can petition your plan to cover an "out-of-network" provider at in-network pricing.
I would also keep in contact with your (or DH's) HR department regarding your coverage ~ they should be able to help you get accurate information.
ALWAYS, write down the name (& ID# if poss) of anyone you talk to, the date & time, and what they said. Call several times and see if you get the same answer. If you get multiple answers ~ ask for a supervisor and ask them to fax you a copy of the policy where it describes midwifery care specifically.
p.s. I used to be the office manager at a free-standing birth center, and part of my duties included verifying benefits. Not to mention that I delivered DS at a birth center and was a hospital transfer for DD (that is also a bundle of dealings). If you want to PM me, I can try to get more specific for you.