The halacha is that if you have a medical question (like whether to be mechalel Shabbos for a choleh, or whether a baby boy is too yellow for milah) then you ask a doctor.
Mrs Plony, NOBODY asks a doctor whether a baby is too yellow for milah. The UNIVERSALLY accepted halacha is that we do NOT ask doctors. If we were to ask the doctors there would be no such thing as a delayed bris for yellowness, and the whole halacha about it would have been long forgotten. We ask only a mohel who has received the tradition from the mohel who trained him, and we disregard the unanimous advice of all doctors that postnatal jaundice is no reason to delay circumcision.