First of all, you have to assume that (a) any of them are still alive; and (b) any of them remember one specific birth 47 years ago.
Isn't it extremely odd that nobody wants to bask in the glory of having been present at the birth of supposedly the most "historic" presidential candidate of all time (not to mention the opportunity for lucrative book deals, interviews, etc.)?
Any medical professional who came forth to discuss the birth would be in violation of medical ethics rules regarding privacy, as well as state and Federal medical privacy laws. Medical professionals cannoth reveal that they treated someone or had them as a patient without that person's consent to such revelation.
Just to give you an example, when my wife gave birth to our son a couple of months ago, the hospital would not even tell friends of ours that she was a patient there when they called in to confirm where to send the flowers.
(a) I don't assume any are alive. I assume they never existed. That is far more believable.
(b) Anyone connected with any major medical facility in Oahu in 1961 would not be oblivious to the Obama/Hawaii connection and would have searched his memory and any accessible hospital records to see if he hadn't been present at the blessed event of the messiah's birth. So everybody in this category has amnesia or doesn't follow the news?
(c) Oh yes, the medical confidentiality canard. If there was a genuine witness, Obama would be begging this witness to come forward and vouch for him, not trying to keep him quiet for no explicable reason.