When Baby is Really Small

A baby can only be given his bris when he is completely healthy.  When he is a preemie, or otherwise small, is he considered unhealthy?

For bris purposes, any baby over 6 pounds can be considered a "full term baby," regardless of how many weeks early he may be born. Barring any other health concerns, the bris should be on time.

A full term baby who weighs less - though almost all full-term babies are over five pounds - can also have the bris on time.

A preemie - fewer than 36 weeks, will almost always have his bris delayed until he gets a little bigger.

Many mohels have a "kabbalah" (an accepted practice passed from teacher to student) not to do a bris on a baby who is under five pounds. I have an ongoing debate with the grandfather of a set of triplets I circumcised many years ago, because he felt I was randomly picking a weight in order to have all three boys be circumcised on the same day (they all had different weights at birth - the brisses were delayed but ended up taking place on the same day). But it isn't random - a five pound baby has a different look than even a 4 lbs. 10 oz. baby.

In my case, the only exceptions I will make in order to circumcize a baby weighing fewer than 5 pounds are:
A. If the baby is full term, and both of his parents happen to be below average size
B. A case such as the triplets, where the baby is a few weeks old, in perfect health, and is gaining 1-2 ounces a day, and he has a brother who is also ready, whose bris is scheduled. If the baby is in the 4 lbs and double digit ounces range, I will consider circumcising him at the same time as his twin/triplet brother.