It is more than that, In cases of the baby being yellow, it is OSSUR to do the bris. I have heard modern medicine does not rule a baby being yellow as unfit for bris, it is the gemarra and shulchan aruch which states that one does not do a bris when the baby is yellow.
This is why it is futile to ask the doctors what is sufficient “non-yellow” for which to do a bris.