29 C.F.R. § 21.109
(f)
(1) Unless an IRB determines otherwise, continuing review of research is not required in the following circumstances:
(iii) Research that has progressed to the point that it involves only one or both of the following, which are part of the IRB-approved study:
(g) An IRB shall have authority to observe or have a third party observe the consent process and the research.
(Approved by the Office of Management and Budget under Control Number 0990-0260)