Laws regarding midwifery in the United States are a constantly changing hodgepodge of state regulations that stipulate everything from who can call herself a midwife to what limits, if any, are placed on practice. There are four general categories of midwife in the US.
Certified nurse-midwives (CNM) are registered nurses with advanced degrees in midwifery (since 2010, at master's or doctoral level) from university-based programs accredited by the Accreditation Commission for Midwifery Education. They are certified by the American Midwifery Certification Board to provide a wide scope of women's health care, including primary and gynecological care, family planning and care through pregnancy and childbirth, as well as care of the newborn. They are licensed in all 50 states and the US territories, practicing in hospitals, clinics and birth centers and at home births, and can prescribe a wide range of medications. They do not perform surgical births (cesarean section or vacuum- or forceps-assisted vaginal deliveries) but may assist obstetricians in such deliveries.
Certified midwives (CM) have the same midwifery and women's health training and scope of practice as certified nurse-midwives, but they are not registered nurses. They can practice in hospitals and birth centers and attend home births, but at this writing only New Jersey, New York, Rhode Island, Delaware and Missouri recognize the CM credential.
Certified Professional Midwives
Certified professional midwives (CPM) have a high school diploma or equivalent (required for CPMs credentialed after September 2012) and are certified by the North American Registry of Midwives (NARM). They follow one of two educational paths: completion of a midwifery education program accredited by the Midwifery Education Accreditation Council, or completion of NARM's Portfolio Evaluation Process (PEP), an apprenticeship-based pathway that requires no formal didactic educational component (currently, the majority of CPMs in the US are credentialed through PEP). CPMs care for women and babies during pregnancy, childbirth and the postpartum period. They may legally provide care in 28 states (only some of which require licensure) and primarily attend out-of-hospital births. Some states permit CPMs to obtain and administer a limited variety of medications.
Lay or "Traditional" Midwives
These midwives are not licensed or credentialed and may legally care for women in pregnancy and attend childbirth in only a handful of states that do not prohibit their practice.