Brith melah is done on the 8th day after birth , sometimes delayed by illness . Can it be done on day 7?
No it can not. The torah tells us (Leviticus 12-3) that it can only be done from day 8 and on. It is noteworthy that the day of birth is considered the first day, therefore if a baby is born on Tuesday morning, the bris can be done the next Tuesday. Although sometimes we don’t have a choice but to do the bris late due to illness, nevertheless we can not make the bris earlier than the 8th day.
Mazal tov and best wishes