All of my nursing school faculty, including the clinical professor for maternal/child health (a CNM), pronounced it "um-bil-IKE-us", too, so I think that's correct. I can't bring myself to say it, though!
In my pre-nursing life I was a technical writer, so I'm a bit of a stickler about grammar and spelling, but what patients say doesn't bother me as long as we're communicating adequately. Regional accents don't get to me, either; I actually like them. It does bug me immensely when nurses or doctors pronounce things incorrectly, such as the aforementioned "oooopherectomy" or "nuke-yu-lar."