Complementary Growth: Midwives and Obstetrician-Gynecologists in the US Maternity Care System

Persistent shortages in the US maternity care workforce have prompted repeated policy calls to expand access to midwifery. Federal and professional organizations have positioned midwives as potential substitutes for obstetrician-gynecologists to fill gaps created by declining obstetric capacity. Economic theory suggests professions may operate as substitutes, complements, or independently. If midwives and obstetrician-gynecologists are substitutes, growth in one would offset the other; if complements, both would expand together; and, if independent, workforce changes would be unrelated. Determining which relationship exists is critical for efficient workforce investment and planning, particularly as national efforts to address maternity care shortages intensify. The aim of this study was to measure the correlation between the growth of the midwifery and obstetrician-gynecologist workforces to determine whether they have functioned as substitutes, compliments, or independent professions within the US maternity care system.

We conducted a retrospective analysis of workforce changes between 2011 and 2023 using data from the Area Health Resources File, the American Midwifery Certification Board, and CDC WONDER. Workforce density was calculated as providers per 1,000 live births. Correlation coefficients between changes in midwife and obstetrician-gynecologist density were estimated nationally and stratified by state regulatory environments.

Between 2011 and 2023, both obstetrician-gynecologist density and midwife density increased. Changes in midwife and obstetrician-gynecologist density were positively correlated (r = 0.63; P <  .001), indicating complementary workforce growth. This relationship persisted across states with independent and restricted midwifery regulations.

Midwives and obstetrician-gynecologists function as complementary professions in the US maternity workforce, with growth in one profession associated with growth in the other. Workforce planning and policy should account for the complementary relationship between midwives and obstetrician-gynecologists. Integrated funding strategies, reimbursement models, and workforce projections may better support access to high-quality maternal health care.