The day the child is born counts as the first day, thus if the child is born on a Wednesday, he is circumcised on the following Wednesday. Keep in mind that Jewish days begin at sunset, so if the child is born on a Wednesday evening, he is circumcised the following Thursday. Circumcisions are performed on Shabbat , even though they involve the drawing of blood which is ordinarily forbidden on shabbat. As with almost any commandment, circumcision can be postponed for health reasons. Jewish law provides that where the child's health is at issue, circumcision must wait until seven days after a doctor declares the child healthy enough to undergo the procedure.
Circumcision involves surgically removing the foreskin of the penis.
Circumcision performed by a regular physician does not qualify as a valid brit milah, regardless of whether a rabbi says a blessing over it, because the removal of the foreskin is itself a religious ritual that must be performed by someone religiously qualified. This is referred to as hatafat dam brit. While the circumcision is performed, the child is held by a person called a sandek. In English, this is often referred to as a godfather. It is an honor to be a sandek for a bris.