42 CFR §414.54

1. (a)For services furnished after December 31, 1991, allowed amounts under the fee schedule established under section 1833(a)(1)(K) of the Act for the payment of certified nurse-midwife services may not exceed 65 percent of the physician fee schedule amount for the service.
2. (b)For certified nurse-midwife services furnished on or after January 1, 2011, allowed amounts may not exceed 100 percent of the physician fee schedule amount that would be paid to a physician for the services.