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

Abstract

Introduction

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.

Methods

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.

Results

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.

Discussion

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.

INTRODUCTION

Since 1999, certified nurse‐midwives (CNMs) and certified midwives (CMs), hereafter referred to as midwives, have been proposed as a solution to the maternity problems in the United States. The American Public Health Association released a position paper supporting increasing access to midwifery services in 1999 and echoed the call in a 2011 policy statement on reducing shortages of maternity care providers and maternal mortality. ¹ , ² For the past 10 years, the American College of Obstetricians and Gynecologists has recommended team‐based care models that include midwives as a strategy to ensure quality, efficiency, and value in health care systems. ³ In 2019, the March of Dimes released a position statement supporting the expansion of midwifery practice. ⁴ The following year, the National Academies emphasized the need for midwives to practice to the fullest extent of their training. ⁵ Likewise, in 2021, the Health Resources and Services Administration (HRSA) included midwives in the calculation for Maternity Care Target Areas to address provider shortages. ⁶ Collectively, these calls frame midwives as substitutes for obstetrician‐gynecologists, with the expectation that midwives can fill clinical gaps created by declining obstetric capacity.

1. QUICK POINTS

• ✦Calculating maternity workforce density as clinicians per 1,000 births accounts for declining birth volume, providing a more accurate picture of workforce trends than raw clinician counts alone.
• ✦Applying the economic framework of substitutes, compliments, and independent services to maternity workforce analysis offers an approach to understanding multidisciplinary workforces.
• ✦The growth of state midwifery and obstetrician‐gynecologist workforces has a strong positive correlation, suggesting a complementary relationship.

Midwifery in the United States

The CNM and CM credentials require graduation from an accredited master's‐level midwifery education program and passage of a national certification examination administered by the American Midwifery Certification Board (AMCB). ⁷ CNMs hold a prior nursing licensure, whereas CMs enter midwifery without nursing credentials. The scope of practice for AMCB‐certified midwives encompasses primary care for women across the life span, including prenatal, intrapartum, and postpartum care; gynecologic and reproductive health care services; and newborn care. Midwives attended 12% of US births in 2024. ⁸

State‐level regulation of AMCB‐certified midwifery practice demonstrates substantial heterogeneity across the United States. Although CNMs are licensed to practice in all 50 states and the District of Columbia, CMs face more restricted recognition, with licensure available in 10 states in 2023. ⁹ The degree of practice autonomy also differs markedly; some states grant full practice authority, allowing midwives to practice independently without physician collaboration or supervision requirements, whereas others mandate varying levels of physician oversight, collaborative practice agreements, or restrictions on practice settings. ⁹ , ¹⁰ Prescriptive authority similarly varies, with some states permitting independent prescribing of all legend drugs, including controlled substances, whereas others impose limitations on formulary scope or require physician involvement in prescriptive practices. These regulatory disparities create significant barriers to practice mobility, affect workforce distribution, and contribute to geographic inequities in access to midwifery care. ¹⁰ , ¹¹

Other midwives, primarily certified professional midwives (CPMs) credentialed through the North American Registry of Midwives, operate under different regulatory frameworks than their AMCB‐certified counterparts. ¹² Although CNMs are typically regulated under advanced practice nursing statutes, CPMs are often governed by separate direct‐entry midwifery statutes or remain unregulated. This bifurcated regulatory approach reflects divergent educational pathways, practice philosophies, and historical development of the midwifery profession in the United States. CPMs attended approximately 1.4% of births in 2024, predominantly in out‐of‐hospital settings, including home births and freestanding birth centers. ⁸ The distinct regulatory treatment creates challenges for workforce planning and care coordination because midwives face different requirements for licensure, scope of practice, prescriptive authority, collaborative agreements, and professional liability coverage despite serving similar populations of childbearing families. ¹³

Substitutes and Compliments: Economic Theory

To understand whether midwives can address projected obstetrician‐gynecologist shortages, it is essential to clarify the relationship between the 2 professions. In health care workforce planning, supply‐and‐demand theory helps predict changes in supply of and demand for health care workers. ¹⁴ The HRSA uses supply‐and‐demand models to predict shortages of obstetrician‐gynecologists using the size of the workforce as the supply of care and the use of obstetric services as the demand for care. ¹⁵ When using supply‐and‐demand models, workers may act as substitutes or complements or be independent of each other. Substitutes are workers who are interchangeable; that is, they can replace each other because they perform similar functions. ¹⁶ In contrast, complements are workers whose productivity is increased when they work together because they enhance each other's value. Finally, 2 workers may be independent, meaning that demand for one has no systematic relationship to demand for the other.

The expectation that midwives can serve as substitutes for obstetrician‐gynecologists is valid to the extent that the skills of midwives and obstetrician‐gynecologists overlap. The International Confederation of Midwives argues that midwives can provide approximately 87% of essential sexual, reproductive, maternal, newborn, and adolescent health care services to women and newborns. ¹⁷ This framing of midwives as physician substitutes is echoed by physician groups’ statements of opposition to midwifery autonomous practice. ¹⁸ , ¹⁹ Physician arguments focus on hypothetical safety risks of allowing midwives to substitute for obstetrician‐gynecologists because of differences in training and use these claims to support requirements that midwives contract with a physician to legally provide care. ²⁰ , ²¹ These claims are not backed by evidence and can mask an underlying economic concern: that autonomous midwifery shifts market share and control of maternity care away from physicians. ²² In this way, opposition from physicians reinforces the same substitution logic but recasts midwives as competitors whose autonomy threatens the physician role.

Although midwives are sometimes framed as substitutes for obstetrician‐gynecologists, the most recent HRSA Report on the maternity care workforce treats the professions as independent. The analysis forecasted a shortage of 9,890 obstetrician‐gynecologists by 2037 and an excess of 4,670 midwives within the same period but did not suggest the surplus of midwives could address the shortage of obstetrician‐gynecologist services. ²² Federal funding to expand midwifery and obstetrics‐gynecology education also treats them as independent workforces. Funding for midwifery education is authorized through 42 US Code § 296j as part of advanced education for nursing, whereas obstetrician‐gynecologist funding is part of the graduate medical education funding through Medicare under 42 US Code 1395ww(h). ²³ , ²⁴

Measuring the Relationship Between Midwifery and Obstetrician‐Gynecologist Workforces

Although an overlap exists, whether the midwifery workforce growth is a complement to, a substitute to, or independent of the obstetrician‐gynecologist workforce has implications for maternity workforce development. If the professions' growth is independent, policies and funding designed to expand midwifery will not result in a change in the obstetrician‐gynecologist workforce. If midwifery and obstetrician‐gynecologist workforces grow as substitutes, programs that expand each workforce separately may unintentionally work at cross purposes. Conversely, if midwives and obstetrician‐gynecologists grow as complements, efforts to expand only one profession could fall short of addressing overall system needs. Clarifying this relationship is essential, because mischaracterizing midwives’ workforce growth may result in designing policies that fail to resolve, and may even exacerbate, maternity care shortages.

One method to evaluate whether midwives are substitutes, complements, or independent of obstetrician‐gynecologists is to measure the correlation between the growth of the midwifery workforce and the growth of the obstetrician‐gynecologist workforce. By measuring changes in workforce density (providers per birth) rather than the raw number of providers, this analysis can account for changes in demand. For this analysis, a positive correlation would indicate that both workforces grow together and suggest that they are complements. A negative correlation, on the other hand, would demonstrate that one workforce decreases as the other increases, which is the pattern for substitutes. ²⁵ If there were no correlation, the findings would suggest the 2 workforces grow independently. The objective of this study, therefore, was to measure the correlation between the growth of the midwifery and obstetrician‐gynecologist workforces.

METHODS

This retrospective study examined the change in maternity care workforce in each state between 2011 and 2023. These dates were selected because 2011 was when the American Public Health Association recommended increasing the maternity workforce, and 2023 is the most recent year for which workforce data were available at the time of analysis. ² This study does not meet the definition of human participant research and is, therefore, exempt from institutional review board approval. We used the Strengthening the Reporting of Observational Studies in Epidemiology statement and checklist to guide the reporting of this observational study. ²⁶

Data Sources

Data for the midwifery workforce and obstetrician‐gynecologist workforce in 2011 were available in the Area Health Resources File, 2011‐2012. ²⁷ We used the most recent data available for obstetrician‐gynecologists from the Area Health Resources File, 2023‐2024. The source for information about midwives in the Area Health Resources File changed between 2011 and 2023. To ensure a consistent count, we used the AMCB count of midwives, which is the same source used in the Area Resource File, 2011‐2012. We used the number of midwives reported as certified by the AMCB as of August 2023. ²⁸ Although these data sources do not limit the workforce to those who attend births, they were the best available for the analysis. Only about three‐quarters of midwives report working as a midwife, and increasing proportions of obstetrician‐gynecologists are choosing subspecialty practice. ²⁹ , ³⁰ It is essential that both midwives and obstetrician‐gynecologists fill roles that do not include birth attendance, such as educator, administrator, or subspecialty, and the total workforce should be measured when considering workforce size. The use of all workers in a workforce, regardless of role, aligns with the HRSA Bureau of Health Workforce methods for modeling the size of the maternity workforce. ¹⁵

Data Analysis

All analyses were conducted in Microsoft Excel. The maternity care workforce for each state and the District of Columbia was described as the number of obstetrician‐gynecologists, the number of midwives, and the total number of providers.

To determine whether midwives and obstetrician‐gynecologists function as substitutes or complements, the numbers of each provider type were converted to a density of providers for each state and the District of Columbia by measuring the number of providers per 1,000 live births in the state. This method was chosen because the fertility rate decreased from 63.2 to 54.5 births per 1,000 females aged 15 to 44 years during this time frame, and state fertility rates vary. ³¹ States with higher fertility rates have more births relative to their population size, meaning that using population as the denominator could undercount provider need in high‐fertility states. Demand for well‐woman and other primary care services provided by obstetrician‐gynecologists and midwives is more likely to be constant based on population. Therefore, using the number of live births as the denominator allows this analysis to account for variation in maternity‐specific demand across states, which is particularly important, given geographic disparities in maternity care access and workforce shortages. Using population estimates as the denominator, compared with births, has been demonstrated to alter the reported midwife density in ways that may obscure meaningful differences in provider availability relative to service demand. ³² Providers attending births are responsive to the number of births rather than the size of the general population, making births a more appropriate denominator for estimating maternity provider density. Data for live births were obtained through CDC WONDER for 2011 and 2023. ⁸

We measured the correlation of change in midwife density with change in obstetrician‐gynecologist density, with a positive correlation indicating complements and a negative correlation indicating substitutes. Correlation is an appropriate first step for an exploratory analysis to determine the association between 2 variables because the extent to which the variables change together is shown. ³³

Existing evidence demonstrates a different distribution of midwives in states with autonomous compared with restrictive midwifery regulation. ¹⁰ To determine whether the regulatory environment was a potential moderator of the correlation in growth between midwives and obstetrician‐gynecologists, we stratified the analysis based on midwifery regulation defined by the American College of Nurse Midwives (ACNM) from the 2023 Midwifery Chartbook, which is based on need for a written collaborative agreement for any part of midwifery practice. ⁹

Finally, we conducted a sensitivity analysis to explore how changes in assumptions about what makes midwifery practice independent may change the results. We based this analysis on prior work that found a different trajectory of midwifery workforce growth in states that adopted 3 policies considered enabling for midwifery. ¹¹ The first, independent practice, was defined as no requirement for a written practice agreement. The second, Medicaid parity, was defined as midwives receiving the same Medicaid reimbursement rates for care compared with a physician. The final policy allowed midwives to admit and discharge their patients to the hospital for care during labor and birth without requiring the signature of a physician. The ACNM found that only 11 states and the District of Columbia had these 3 policies, providing full autonomy. ⁹ We further stratified the remaining states into those that had one or 2 policies, providing limited autonomy, and those with zero enabling policies, providing no autonomy. This study was completed without research funding.

RESULTS

In 2011, 45,229 obstetrician‐gynecologists and 12,383 midwives, for a total of 57,612 maternity providers, existed in the United States (Table 1). In 2023, there were 43,817 obstetrician‐gynecologists and 14,115 midwives, for a total of 57,932 US maternity providers (Table 2). Comparing the workforce in 2011 and 2023, a 3.1% loss of obstetrician‐gynecologists (n = −1412) and a 14% increase in midwives (n = 1732) were experienced, which resulted in a 0.6% increase in overall maternity providers (n = 320). Between 2011 and 2023, the US birth rate decreased 9%, a decrease of 357,573 live births.

Table 1.

Description of Maternity Workforce by State, 2011

State Name	Births	Obstetricians	Midwives	Total Providers	Obstetrician Density	Midwife Density	Total Density
Alabama	59,354	557	62	619	9.38	1.04	10.43
Alaska	11,456	82	94	176	7.16	8.21	15.36
Arizona	85,543	781	246	1,027	9.13	2.88	12.01
Arkansas	38,715	285	32	317	7.36	0.83	8.19
California	502,120	5189	1229	6418	10.33	2.45	12.78
Colorado	65,055	762	356	1118	11.71	5.47	17.19
Connecticut	37,281	792	251	1,043	21.24	6.73	27.98
Delaware	11,257	118	46	164	10.48	4.09	14.57
District of Columbia	9295	236	75	311	25.39	8.07	33.46
Florida	213,414	2272	769	3,041	10.65	3.60	14.25
Georgia	132,409	1347	459	1,806	10.17	3.47	13.64
Hawaii	18,956	257	58	315	13.56	3.06	16.62
Idaho	22,305	153	46	199	6.86	2.06	8.92
Illinois	161,312	2,018	472	2,490	12.51	2.93	15.44
Indiana	83,701	764	148	912	9.13	1.77	10.90
Iowa	38,214	268	85	353	7.01	2.22	9.24
Kansas	39,642	337	74	411	8.50	1.87	10.37
Kentucky	55,370	539	130	669	9.73	2.35	12.08
Louisiana	61,888	790	52	842	12.76	0.84	13.61
Maine	12,704	184	111	295	14.48	8.74	23.22
Maryland	73,093	1156	462	1618	15.82	6.32	22.14
Massachusetts	73,166	1167	513	1,680	15.95	7.01	22.96
Michigan	114,008	1726	353	2,079	15.14	3.10	18.24
Minnesota	68,409	663	266	929	9.69	3.89	13.58
Mississippi	39,860	341	51	392	8.55	1.28	9.83
Missouri	76,117	834	116	950	10.96	1.52	12.48
Montana	12,069	101	41	142	8.37	3.40	11.77
Nebraska	25,720	244	36	280	9.49	1.40	10.89
Nevada	35,296	281	46	327	7.96	1.30	9.26
New Hampshire	12,851	208	121	329	16.19	9.42	25.60
New Jersey	105,883	1549	340	1889	14.63	3.21	17.84
New Mexico	27,289	241	222	463	8.83	8.14	16.97
New York	241,312	3922	1,170	5,092	16.25	4.85	21.10
North Carolina	120,389	1357	416	1773	11.27	3.46	14.73
North Dakota	9527	57	16	73	5.98	1.68	7.66
Ohio	137,918	1792	404	2196	12.99	2.93	15.92
Oklahoma	52,272	409	67	476	7.82	1.28	9.11
Oregon	45,155	545	329	874	12.07	7.29	19.36
Pennsylvania	143,178	2,021	512	2533	14.12	3.58	17.69
Rhode Island	10,960	223	65	288	20.35	5.93	26.28
South Carolina	57,393	649	142	791	11.31	2.47	13.78
South Dakota	11,846	83	38	121	7.01	3.21	10.21
Tennessee	79,588	967	190	1157	12.15	2.39	14.54
Texas	377,445	3429	473	3,902	9.08	1.25	10.34
Utah	51,223	328	155	483	6.40	3.03	9.43
Vermont	6,078	112	70	182	18.43	11.52	29.94
Virginia	102,652	1284	279	1563	12.51	2.72	15.23
Washington	86,976	787	387	1174	9.05	4.45	13.50
West Virginia	20,717	229	69	298	11.05	3.33	14.38
Wisconsin	67,810	727	225	952	10.72	3.32	14.04
Wyoming	7399	66	14	80	8.92	1.89	10.81

Table 2.

Description of Maternity Workforce by State, 2023

State Name	Births	Obstetricians	Midwives	Total Providers	Obstetrician Density	Midwife Density	Total Density
Alabama	57,858	534	66	600	9.2	1.14	10.37
Alaska	9,015	93	111	204	10.3	12.31	22.63
Arizona	78,096	793	280	1,073	10.2	3.59	13.74
Arkansas	35,264	277	49	326	7.9	1.39	9.24
California	400,108	5168	1237	6,405	12.9	3.09	16.01
Colorado	61,494	816	486	1302	13.3	7.90	21.17
Connecticut	34,559	705	220	925	20.4	6.37	26.77
Delaware	10,427	125	44	169	12.0	4.22	16.21
District of Columbia	7896	218	50	268	27.6	6.33	33.94
Florida	221,410	2621	869	3,490	11.8	3.92	15.76
Georgia	125,120	1,408	610	2,018	11.3	4.88	16.13
Hawaii	14,808	238	62	300	16.1	4.19	20.26
Idaho	22,397	156	89	245	7.0	3.97	10.94
Illinois	124,820	1,802	495	2297	14.4	3.97	18.40
Indiana	79,000	738	215	953	9.3	2.72	12.06
Iowa	36,052	278	134	412	7.7	3.72	11.43
Kansas	34,065	328	103	431	9.6	3.02	12.65
Kentucky	51,984	511	144	655	9.8	2.77	12.60
Louisiana	54,927	723	82	805	13.2	1.49	14.66
Maine	11,627	184	119	303	15.8	10.23	26.06
Maryland	65,594	1,013	333	1346	15.4	5.08	20.52
Massachusetts	67,093	1,085	465	1,550	16.2	6.93	23.10
Michigan	99,124	1543	508	2,051	15.6	5.12	20.69
Minnesota	61,715	740	412	1152	12.0	6.68	18.67
Mississippi	34,459	326	37	363	9.5	1.07	10.53
Missouri	67,123	780	137	917	11.6	2.04	13.66
Montana	11,078	123	63	186	11.1	5.69	16.79
Nebraska	24,111	240	55	295	10.0	2.28	12.24
Nevada	31,794	322	65	387	10.1	2.04	12.17
New Hampshire	11,936	188	125	313	15.8	10.47	26.22
New Jersey	101,001	1462	348	1,810	14.5	3.45	17.92
New Mexico	20,951	223	213	436	10.6	10.17	20.81
New York	203,612	3,480	1,065	4545	17.1	5.23	22.32
North Carolina	120,082	1416	526	1942	11.8	4.38	16.17
North Dakota	9647	78	21	99	8.1	2.18	10.26
Ohio	126,896	1592	500	2,092	12.5	3.94	16.49
Oklahoma	47,909	397	73	470	8.3	1.52	9.81
Oregon	38,298	598	395	993	15.6	10.31	25.93
Pennsylvania	126,951	1778	559	2337	14.0	4.40	18.41
Rhode Island	9,805	197	89	286	20.1	9.08	29.17
South Carolina	57,729	642	139	781	11.1	2.41	13.53
South Dakota	11,201	96	35	131	8.6	3.12	11.70
Tennessee	83,021	866	315	1181	10.4	3.79	14.23
Texas	387,945	3542	617	4159	9.1	1.59	10.72
Utah	45,019	346	194	540	7.7	4.31	11.99
Vermont	5,065	105	88	193	20.7	17.37	38.10
Virginia	92,649	1141	383	1524	12.3	4.13	16.45
Washington	80,932	834	520	1354	10.3	6.43	16.73
West Virginia	16,606	206	72	278	12.4	4.34	16.74
Wisconsin	59,754	681	273	954	11.4	4.57	15.97
Wyoming	5,990	61	25	86	10.2	4.17	14.36

During this time, the obstetrician‐gynecologist provider density increased from 11.4 per 1,000 live births to 12.2 per 1,000 live births, the midwife provider density increased from 3.13 per 1,000 live births to 3.93 per 1,000 live births, and the combined workforce (midwives and obstetrician‐gynecologists) provider density increased from 15.57 per 1,000 live births to 16.11 per 1,000 live births. Workforce density changes in individual states varied, with 11 states experiencing a decrease in obstetrician‐gynecologist provider density, 7 states experiencing a decrease in midwife provider density, and 5 states experiencing a decrease in combined workforce provider density (Table 3).

Table 3.

Change in Maternity Workforce Density, 2011‐2023

State	Obstetrician Change	Midwife Change	Total Change
Alabama	0.32	0.12	0.43
Alaska	0.84	1.24	1.53
Arizona	0.98	0.49	1.47
Arkansas	0.18	0.6	0.77
California	0.31	0.08	0.25
Colorado	1.76	1.43	3.41
Connecticut	0.1	−0.76	−0.79
Delaware	1.58	0.01	1.42
District of Columbia	3.19	−2.24	0.50
Florida	2.1	0.47	2.57
Georgia	1.11	1.29	2.40
Hawaii	−0.21	0.22	−0.20
Idaho	0.14	1.86	2.15
Illinois	−0.38	0.33	−0.14
Indiana	0.28	0.92	1.22
Iowa	0.68	1.49	2.16
Kansas	0.49	0.98	1.43
Kentucky	0.32	0.06	0.40
Louisiana	0.18	0.64	0.71
Maine	0.59	0.37	0.56
Maryland	−1.07	−1.87	−3.17
Massachusetts	0.54	−0.72	−0.22
Michigan	−0.16	1.7	1.39
Minnesota	1.61	2.66	4.05
Mississippi	0.32	−0.25	0.02
Missouri	0.42	0.47	0.85
Montana	1.89	2.13	4.09
Nebraska	1.02	0.86	1.91
Nevada	1.15	0.44	1.54
New Hampshire	−0.52	1.26	0.44
New Jersey	0.05	0.03	0.03
New Mexico	−0.09	−0.1	−0.83
New York	0.25	−0.46	−0.30
North Carolina	1.52	1.04	2.60
North Dakota	2.35	0.32	2.68
Ohio	0.01	0.82	0.78
Oklahoma	0.41	0.33	0.73
Oregon	1.72	2.06	3.36
Pennsylvania	0.03	0.62	0.54
Rhode Island	−0.09	1.77	1.46
South Carolina	0.81	0.09	0.95
South Dakota	1.16	−0.07	1.16
Tennessee	0.12	1.88	2.07
Texas	1.23	0.44	1.67
Utah	0.85	1.08	2.02
Vermont	0.01	4.88	3.87
Virginia	−0.7	1.56	0.68
Washington	0.74	1.49	2.21
West Virginia	0.06	0.47	0.52
Wisconsin	0.16	0.91	1.04
Wyoming	−0.93	1.44	0.53

Density measures as providers per 1,000 live births.

The correlation between changes in midwife and obstetrician‐gynecologist density was moderately positive (r = 0.38; P =  .006), indicating the workforces operate as complements growing and shrinking together. The positive correlation was confirmed for states with both independent midwifery regulation (r = 0.35; P =  .011) and restricted midwifery regulation (r = 0.72; P <  .001), although states with restricted midwifery regulation had a strong positive correlation. Full results are available in Table 4.

Table 4.

Correlation of Change in Density for Midwifery and Obstetrician‐Gynecologist Workforces, 2011‐2023

Analysis	N	Correlation Coefficient	95% CI	P Value
Main analysis
National	51	0.38	0.12 to 0.59	.006
Restricted states	25	0.72	0.55 to 0.83	<.001
Independent states	26	0.35	0.09 to 0.57	.011
Sensitivity analysis
Fully autonomy	12	−0.01	−0.28 to 0.27	.951
Limited autonomy	28	0.53	0.30 to 0.70	<.001
No autonomy	11	0.56	0.33 to 0.72	<.001

In the sensitivity analysis, we stratified the analysis based on level of midwifery autonomy to assess the robustness of our findings. When we limited the analysis to states with full midwifery autonomy, there was no statistically significant correlation between midwifery and obstetrician‐gynecologist workforce changes (r = −0.01; P =  .951). This finding suggests the 2 workforces were acting independently, but we cannot rule out a type II error because of the small sample size. We found a moderate positive correlation for states with limited autonomy (r = 0.53; P <  .001) and states with no autonomy (r = 0.56; P <  .001). The presence of a statistically significant positive correlation in these smaller subgroups supports the robustness of the complementary relationship observed in the main analysis.

DISCUSSION

Findings from this study indicate that the midwife and the obstetrician‐gynecologist workforces appear to operate as market complements, meaning that at the state level, their overall density increases or decreases together. This finding was true both for states with independent midwife regulation and states with restricted midwife regulation. At the national level, both obstetrician‐gynecologist and midwife provider density increased over the study period despite a modest decline in the raw number of obstetrician‐gynecologists, reflecting the parallel decrease in number of live births. This finding adds to the understanding of the forces that contribute to the growth of the midwifery workforce.

Prior studies describing variation in the midwife workforce have included the obstetric workforce as a control variable, acknowledging an association with midwifery workforce outcomes and the potential for confounding. ³⁴ , ³⁵ The current findings extend this work by explicitly examining how the 2 workforces change in relation to one another. Our analysis identifies correlated growth but does not determine whether growth in one workforce causes growth in the other or whether both respond to shared external forces. Other work examining changes in the midwifery workforce in isolation documented substantial variation in where and when the workforce supply increases, relating to regulatory context. ¹⁰ , ²⁰ The variations identified in these prior works may reflect conditions that support expansion of maternity care teams rather than midwives alone.

One potential reason midwives and obstetrician‐gynecologists have complementary growth is that hiring midwives allows obstetrician‐gynecologist practices to task‐shift routine care to midwives and focus physician time for higher‐reimbursement tasks, such as procedures and surgeries. Although midwives provide many services that are also provided by obstetrician‐gynecologists, midwives are not surgeons and, therefore, do not perform the procedures with the highest reimbursement rates. Reimbursement rates for global maternity care are very low in many states, resulting in revenue losses for providing standard maternity care, especially for Medicaid recipients. ³⁶ Low reimbursement for standard care may act as a cost‐saving incentive for practices to task‐shift standard care to midwives and other advanced practice clinicians, who typically have lower salaries, overhead costs, and malpractice premiums than obstetrician‐gynecologists. ³⁷

Another factor influencing the midwives and obstetrician‐gynecologists functioning together as complements during this time frame is that addressing the shortage of maternity care workers reduces economic pressure to act as substitutes. Federal programs designed to attract advanced practice nurses and physicians to work in health care provider shortage areas, such as the National Health Service Corps scholarship and loan repayment programs, may have resulted in a parallel increase in both midwives and obstetrician‐gynecologists. Data to test these correlations outside this window of workforce shortage were not available.

Finally, it is possible states have other policies, beyond the written practice agreement requirements, that limit the growth of the midwifery workforce. Prior work identified 2 additional policies that were associated with lower midwife‐attended birth rates, Medicaid reimbursement adjustments, and restricting midwives’ hospital admitting privleges. ¹¹ The sensitivity analysis in this study tested the stability of the results if we changed our comparison to states with and without these 3 policies. There was no correlation between the 2 workforces in states that grant full autonomous practice to CNM/CMs, suggesting future work should be developed to better understand the effects of these policies on workforce growth and access to care. The American Public Health Association recommended in 1999 that states set entry to practice for midwifery based on education and certification. ¹ The continued existence of regulatory restrictions on midwifery practice 25 years later may be contributing to the continued shortage of access to maternity care.

Policy Implications

These results highlight policy considerations for expanding the maternity care workforce. For example, given the complementary nature of the workforces, there may be value in workforce development investments that link the 2 professions rather than treat them as silos. Similarly, workforce projections may be improved by considering the complementary nature of workforce growth. Facilities that hire midwives may benefit from reimbursement structures that recognize midwives as complementary to obstetricians‐gynecologists rather than as substitutes.

Strengths and Limitations

A particular strength of this study is the comparison of workforce growth over a 12‐year time span, preventing misinterpretation of year‐to‐year variation as growth. Taking this longer view prevents this study from providing a more nuanced description of workforce change. Another strength is the use of the number of live births in the state rather than number of females aged 15 to 44 years in the state as the denominator for workforce density. Because most midwives in clinical practice attend births, this measure can capture changes that may be obscured by population‐based measures, given the decrease in fertility rate from 63.2 to 54.5 births per 1,000 women aged 15 to 44 years over the period. ³² This measure may be less sensitive for obstetrician‐gynecologists because these providers are increasingly entering subspecialty practices. ³⁰

As with prior workforce growth analyses, changes in provider counts may not fully capture changes in clinical availability, particularly given evidence that approximately one‐quarter of the midwifery workforce is not engaged in clinical practice. However, among midwives who work full‐time, nearly 80% attend births. ²⁹ This analysis uses a summary measure of the change in density of midwives and obstetrician‐gynecologists relative to the changes in the number of births. This method is adequate for preliminary examination of the presence of a relationship but should not be interpreted as representing the complete maternity care workforce in each state. Future analyses including other types of providers who attend birth, such as family medicine physicians and physician assistants, are needed to improve understanding of identified correlations, which will provide more accurate estimates of state maternity workforces.

This analysis relies on state‐level reporting of workforce, which does not reflect local variations in practice. Analysis of local variation, such as rural and urban differences or county‐level distribution, may reveal specific geographic patterns. Additionally, state‐level aggregation cannot capture cross‐border practice patterns, including clinicians who maintain licenses in multiple states or provide telehealth services across state lines, potentially misrepresenting actual access to care.

CONCLUSION

Despite repeated calls since 1999 to expand midwifery as a solution to obstetrician‐gynecologist shortages, current workforce policies view midwives and obstetrician‐gynecologists as independent professions with separate projections and funding. This analysis suggests these professions are economic complements, with growth in one associated with growth in the other. Mischaracterizing their relationship as independent or substitutes risks inefficient workforce planning and missed opportunities to strengthen maternity care capacity. Public health care policy should move beyond this fragmented approach and adopt strategies that recognize and support the complementary roles of midwives and obstetrician‐gynecologists in meeting national maternity care needs.

CONFLICT OF INTEREST

The authors have no conflicts of interest to disclose.