It varies state by state. It also depends on the physician you are working with. A great resource on something like this is ACNM website, they actually address issues like this in their "Standards for Practice of Midwifery" document. The last section:
MIDWIFERY PRACTICE MAY BE EXPANDED BEYOND THE ACNM CORE COMPETENCIES TO INCORPORATE NEW PROCEDURES THAT IMPROVE CARE FOR WOMEN AND THEIR FAMILIES. The midwife:
1. Identifies the need for a new procedure taking into consideration consumer demand, standards for safe practice, and availability of other qualified personnel.
2. Ensures that there are no institutional, state, or federal statutes, regulations, or bylaws that would constrain the midwife from incorporation of the procedure into practice.
3. Demonstrates knowledge and competency, including: a) Knowledge of risks, benefits, and client selection criteria. b) Process for acquisition of required skills. c) Identification and management of complications. d) Process to evaluate outcomes and maintain competency.
4. Identifies a mechanism for obtaining medical consultation, collaboration, and referral related to this procedure.
5. Maintains documentation of the process used to achieve the necessary knowledge, skills and ongoing competency of the expanded or new procedures.
Source: Division of Standards and Practice Approved: ACNM Board of Directors, March 8, 2003; Revised and Approved: ACNM Board of Directors, December 4, 2009
(Supersedes the ACNM's Functions, Standards and Qualifications, 1983 and Standards for the Practice of Nurse-Midwifery 1987, 1993. Standard VIII has been adapted from the ACNM's Guidelines for the Incorporation of New Procedures into Nurse-Midwifery Practice)