Think about the things happening in those early days and impact on baby's
feeding behaviors.  Circ - baby shuts down.  Milk comes in - landscape of
breast changes and confuses some kids.  Bili goes up, physiologic and
complicated by poor feeding etc.
- response to feeding gets worse.  A lot of this happens on day 2 & 3.
Mother's hormones are bouncing off the ceiling and floor, she's weepy and
not able to cope very well, learning new tasks.  It's a wonder it works at
all!

I had always thought that Jewish circ was done at 7 days because natural
vitamin K levels peak about then ( and the ancients found that out by trial
and error with bleeding problems).  Maybe another factor was that
breastfeeding was getting pretty well established by day 7 and our
observant Jewish ancestors picked up on the fact that baby continued to
feed well if circ done on day 7, but before that it interferred.  Who
knows.  Kathy D. care to comment?  Sincerely, Pat in SNJ