I always wait until my patients are six months.
It is possible to neuter as young as 6-8 weeks. However the reason many veterinarians wait is that older neonates are able to handle anesthetics better than very young neonates.
Since this is an elective procedure, why not wait until it is safer to do the surgery? This gives the heart/circulatory system/kidneys/liver a chance to mature and metabolize drugs quicker and easier.
Dr. Van Lienden
Dr. Raymond Van Lienden DVM
The Animal Clinic of Clifton
12702 Chapel Road, Clifton
Virginia, U.S.A. 20124