Evaluation of a Public-Private Certified Nurse-Midwife Maternity Program for Indigent Women

Transcription

1 Evaluation of a Public-Private Certified Nurse-Midwife Maternity Program for Indigent Women Dennis Lenaway, PhD, Thomas D. Koepsell, MD, MPH, Thomas Vaughan, MD, MPH, Gerald van Belle, PhD, Kirkwood Shy, MD, and Federico Cruz-Uribe, MD, MPH Introduction A critical need exists to develop innovative and effective maternity programs to overcome the various obstacles to quality perinatal care for the medically indigent.l1 The Institute of Medicine has recommended expanding the variety of settings available for care, training more nurse-midwives, reducing personal and cultural obstacles, and addressing financial and malpractice issues.5 Certified nurse-midwives are increasingly being used in a number of birth settings, including hospitals, HMOs, birth centers, and public health agencies." The use of certified nurse-midwives in maternity care is thought to offer several advantages relative to physician-managed care, such as lower costs, increased client participation in prenatal care, minimized intervention during delivery, and more attention to psychosocial issues. Increased use of nursemidwives in public and private settings has generated the need to evaluate these various programs. There is a paucity of research evaluating certified nurse-midwife programs in public health settings. Early descriptive studies of the Frontier Nursing Service lacked a suitable comparison group.9-l' More recent before-after studies of public health certified nurse-midwife programs have involved selection bias'2 and small sample sizes with uncontrolled communitylevel variation'3 factors affecting interpretation of their results. Knowledge of the effectiveness of public health certified nurse-midwife programs is incomplete. We undertook a population-based quasi-experimental evaluation of a county-wide public health certified nurse-midwife program for medically indigent women to assess its impact on prenatal care, antepartum complications, and birth outcomes. Background In Colorado, the Governor's Task Force on Prenatal, Labor, and Delivery Care determined that maternity care for low-income women was unacceptable and noted that 1 in 4 pregnancies did not involve appropriate prenatal and delivery care. The task force recommended that the public sector expand its role in assuring adequate maternity services through community-based models. Similarly, a community task force in Boulder County recognized that insufficient maternity services were available to low-income women. Briefly, the model of care developed by the task force and initiated in April 1987 was a public/private partnership relying on certified nurse-midwives as the principal providers of prenatal, delivery, and postpartum care for low-income women. The nurse-midwives were employed by the county health department and medically supervised by private physicians (board certified in obstetrics and gynecology) contracted for this service. Patients were referred to the health department for financial and medical risk screening. The lowrisk, low-income women who qualified for the program received their prenatal care through health department clinics with services provided by certified nurse-midwives, nurse practitioners, and public health nurses guided by protocols provided by the contracting physicians. Any patient developing a high-risk condition or complication was transferred to direct physician care. Routine vaginal deliveries were attended by the certified nurse-midwives at either of the 2 local hospitals; in the event of a labor or Dennis Lenaway is with the Boulder County Health Department, Boulder, Colo. Thomas D. Koepsell, Thomas Vaughan, and Kirkwood Shy are with the Department of Epidemiology, University of Washington, Seattle. Thomas Vaughan is also with the Program in Epidemiology, Fred Hutchinson Cancer Research Center, Seattle; Kirkwood Shy is also with the Department of Obstetrics and Gynecology, University of Washington. Gerald van Belle is with the Departments of Environmental Health and Biostatistics, University of Washington, Seattle. Federico Cruz-Uribe is with the Tacoma-Pierce County Health Department, Tacoma, Washington. Requests for reprints should be sent to Dennis Lenaway, Boulder County Health Department, 3450 Broadway, Boulder, CO This paper was accepted March 28, American Journal of Public Health 675

2 delivery complication necessitating physician care, however, the nurse-midwife transferred patient management to the physician. Follow-up postpartum care was provided by the nurse-midwives at the health department clinics. We hypothesized that this intervention would be associated with significant improvements in the process and outcomes of perinatal care. Methods Study Design This study used a population-based quasi-experimental design comparing one intervention county with 2 nonintervention control counties (designated counties A and B). The 2 comparison counties were selected primarily for sociodemographic similarity and absence of any communitywide intervention strategies. The intervention and comparison counties are contiguous and represent mixed suburban and rural populations. The study included all medically indigent women who resided in the 3 study counties and delivered a live-born singleton infant during the period September 1, 1989, through December 31, Participation in the health department's certified nursemidwife program was not a requirement for inclusion in the study population, so the evaluation results were affected by the program's coverage of the target population as well as its impact on those served. For the purposes of this study, medical indigency was defined as being registered with either Medicaid or the Colorado Indigent Care Program for financial assistance at the time of delivery. Enrollment in these assistance programs was found to be similar among the 3 study counties. Data Collection The primary source for data was birth certificates obtained from the Vital Statistics Section of the Colorado Department of Public Health and Environment. The state Medicaid program and the Colorado Indigent Care Program provided lists of participants for linkage with birth certificate files. The accuracy ofbirth record information was not independently evaluated for this study. Sociodemographic variables, taken directly from the birth record, included maternal age, race/ethnicity, education, marital status, employment during pregnancy, and alcohol and tobacco use during pregnancy. Maternal age was recoded into 3 categories: less than 20 years, 20 to 34 years, and 35 years or more. Women of Hispanic ethnicity were separated from Blacks and White non-hispanics. Asians, Blacks, and all remaining racial groups were labeled as "other." Marital status, alcohol and tobacco use during pregnancy, employment during pregnancy, month prenatal care began, and number of prenatal visits were also taken directly from the birth record. We were unable to obtain a valid measure of parity given the large number of missing values (approximately half) in the primary data furnished. A modified version of the Kessner index'14"5 was used in assessing adequacy of prenatal care. The Kessner index is derived from the total number of prenatal visits and the trimester in which care began, adjusted for gestational age at delivery. The index provides a summary measure in 3 categories: adequate, intermediate, or inadequate. For this analysis, the index was collapsed into a dichotomous outcome variable: adequate vs less than adequate prenatal care.'6 We included as outcomes the complications of anemia, pregnancy-induced hypertension, and gestational diabetes. These complications were selected a priori since they commonly occur during the antenatal period and are thought to be amenable to appropriate prenatal intervention. Also included from the birth certificate were stimulation and/or induction of labor by the birth attendant and delivery method, along with information on vaginal birth after cesarean. The birth outcomes gestational age, 5-minute Apgar score, and birthweight were included in this analysis. A 5-minute Apgar score of 8 was used as a cutoff to allow for clustering of scores near the top of the Apgar scale.'7 Statistical Analysis In this study, the data were derived from community-level allocation, rendering invalid the usual assumptions of independent individual-level observations We used a logistic-binomial random-effects regression model for distinguishable data (EGRET Software, Seattle, Wash) to estimate crude and adjusted odds ratios (ORs) and their associated 95% confidence intervals (CIs). The random-effects model assumed that the study counties could hypothetically be regarded as a random sample of all possible counties available for study. The model considered each study outcome separately as a dependent variable and included an independent county variable to account for any community-level variation. Assessment of effect modification (interaction) preceded any strategy to assess confounding associated with the covariates of maternal age, race, education, marital status, employment during pregnancy, and alcohol and tobacco use during pregnancy (included in the model as independent variables). Significance testing of interaction terms (a =.05, likelihood ratio test) was used to screen for effect modification. Potential confounders were initially entered individually into the model to determine their effect on the odds ratio, and then covariates were added sequentially to the model in a forward selection process (and similar backward elimination) to determine any significant change in the odds ratio due to confounding by multiple variables simultaneously. Any change in the odds ratio of 10% or more prompted inclusion of the variable in the model.2' Analyses revealed that none of the potential interaction terms were significant, and there was a negligible effect after multivariate adjustment on the association between intervention status and study outcomes. Therefore, only unadjusted odds ratios are presented here. Results During the 15-month study period, 692 eligible live singleton births were identified in the intervention county, along with 726 and 1373 births in the 2 control counties. Characteristics of the study cohort are shown in Table 1. The intervention county was similar to both control counties with respect to maternal age, employment during pregnancy, and tobacco use. Differences existed between counties in terms of maternal education, alcohol use during pregnancy, and race/ethnicity. Prenatal Care and Antepartum Complications As shown in Table 2, the proportion of women who received no prenatal care was significantly lower in the intervention county than in the control counties (OR = 0.32, 95% CI = 0.12, 0.86). To investigate differences in the onset of prenatal care, we compared late or no prenatal care and found a nearly equivalent proportion among intervention and control women. Women from the intervention county were significantly less likely to have received less than adequate prenatal care, as indicated by the Kessner index, than those 676 American Journal of Public Health

3 TABLE 1-Maternal Characteristics of Study Population in a Quasi- Experimental Study of a Certified Nurse-Midwife Program for Low-Icome Women: Boulder County (Colorado) and Comparison Counties, 1989 through Characteristic (n = 692), (n = 726), (n = 1373), Age, y < Race White Hispanic Other Unknown Education, y < z Unknown Marital Status Married Single Employed During pregnancy Unknown Tobacco used During pregnancy Unknown Alcohol used During pregnancy Unknown pregnant women from the control counties (OR = 0.74, 95% CI = 0.62, 0.90). The proportion of women who received adequate prenatal care among the intervention population was significantly higher than that among the controls (52.5% vs 44.6%). Table 2 shows results of an analysis of the incidence of selected antepartum complications. We found that the risk of developing anemia was considerably lower among the women from the intervention population than among the control women (OR = 0.33, 95% CI = 0.13, 0.84). The occurrence of pregnancy-induced hypertension was found to be elevated among women from the intervention county relative to the controls (OR = 1.68, 95% CI = 1.02, 2.79). We found a nonsignificant difference in gestational diabetes by intervention status (OR = 1.14, 95%, CI = 0.43, 3.03). Delivery and Birth Outcomes As shown in Table 3, the use of induction during labor was found to be significantly higher among the intervention cohort than among the control population (18.2% vs 9.9%; OR = 2.56, 95% CI = 1.94, 3.36). Similarly, the use of labor stimulation among the intervention group significantly exceeded that reported among the control population (14.9% and 10.4%, respectively; OR = 1.73, 95% CI = 1.29, 2.30). Table 3 shows that the proportion of cesarean section deliveries performed in the intervention and nonintervention counties was nearly identical (13.0% and 13.3%, respectively). Among women who had reported that their previous birth involved a cesarean section, a higher proportion of the intervention cohort reported a vaginal birth (47.6% vs 34.7% in the control cohort; OR = 1.72, 95% CI = 0.79, 3.75). Certified nurse-midwives were the principal delivery attendants for births occurring within the intervention county, in sharp contrast to the comparison counties (60.1% vs 10.3% for control A and 3.9% for control B. The occurrence of premature births, as shown in Table 3, was lower among the women from the intervention cohort than among controls, although this difference was not quite statistically significant (5.9% vs 8.0%; OR = 0.72, 95% CI = 0.51, 1.03). Infants from the intervention cohort were less likely to have a low (less than 9) Apgar score at 5 minutes after birth than were infants in the control group (11.1% vs 20.7%; OR = 0.47, 95% CI = 0.37, 0.67). A comparison of the proportion of low-weight births (Table 3), an important indicator of maternal care, suggests an association with intervention status. The proportions differed between the intervention and control groups, (7.1% vs 9.4%), and this difference was close to statistical significance (OR = 0.73, 95% CI = 0.51, 1.02). Discussion The certified nurse-midwife program in Boulder County sought to increase prenatal care access, reduce unnecessary invasive delivery procedures, and improve birth outcomes among medically indigent women. The results of this populationbased quasi-experimental study suggest that the program was instrumental in reducing the number of low-income women who received no prenatal care, in decreasing the risk of acquiring less than adequate prenatal care, and reducing the prevalence of lowweight births, prematurity, and low 5- minute Apgar scores. The program appeared unable to alter the overall risk of cesarean birth, yet it was able to increase the proportion of vaginal births among women with previous cesarean section deliveries. Unexpectedly, the frequency of induction and stimulation of labor was found to be elevated among the intervention cohort. The association between intervention status and prenatal and birth outcomes did not appear to be importantly confounded by maternal risk factors. The finding that 6 of every 10 births were attended by certified nurse-midwives in the intervention county attests to the extent to which the public health program provided indigent maternity care. Since the risk of receiving no prenatal care was shown to be reduced among indigent women, yet access to care in the first trimester did not significantly improve, the certified nurse-midwife program appears to have been only partially successful in overcoming barriers to access. Past studies have shown that Medicaid recipients tend to begin prenatal care late and have fewer visits.22'23 There is a plethora of demographic, socioeconomic, and institutional barriers to early prenatal care among indigent women Even with a concerted program effort, these barriers may still have prohibited early access among women in our study population. Previous studies investigating public certified nurse-midwife programs have found results similar to ours. Levy and coworkers noted an increase in early prenatal care and a sharp decline in the proportion American Journal of Public Health 677

4 TABLE 2-Prenatal Care and the Risk of Antepartum Complications by Intervention Status, in a Quasi-Experimental Study of a Certified Nurse-Midwife Program for Low-income Women: Boulder County (Colorado) and Comparison Counties, 1989 through 1990 (n = 692), (n = 726), (n = 1373), A + B, OR Complication/Prenatal Outcome % % % % (95% Cl)a No prenatal care (0.12, 0.86) Late or no prenatal care (0.81, 1.22) Less than adequate prenatal care (0.62, 0.90) Anemia (0.13, 0.84) Pregnancy-induced hypertension (1.02, 2.79) Gestational diabetes (0.43, 3.03) Note. OR = odds ratio; Cl = confidence interval. arandom-effects logistic regression. TABLE 3-Selected Delivery and Birth Outcomes, by Intervention Status, in a Quasi-Experimental Study of a Certified Nurse-Midwife Program for Low-Income Women: Boulder County (Colorado) and Comparison Counties, 1989 through 1990 (n = 692), (n = 726), (n = 1373), A + B OR Process/Outcome % % % % (95% CI)a Induction (1.94, 3.36) Stimulation (1.29, 2.30) Cesarean section (0.76,1.26) Vaginal birth after cesarean (0.79, 3.75) Prematurity (<37 weeks) (0.51, 1.03) 5-minute Apgar (s8) (0.37, 0.67) Low birthweight (<2500 g) (0.51,1.02) Note. OR = odds ratio; Cl = confidence interval. arandom-effects logistic regression. of deliveries involving no prenatal care in a certified nurse-midwife program serving mainly indigent women.'2 Results from a study in southeastern Georgia indicated a 5- fold increase in the proportion of low- and moderate-income women receiving early prenatal care after initiation of a certified nurse-midwife program, along with a concomitant drop in the percentage who lacked access to any prenatal care.'3 The incidence of anemia among women from the intervention county was reported to be significantly lower than that among women from the control counties, whereas differences in gestational diabetes were equivocal, and pregnancy-induced hypertension was shown to have a significantly higher rate. What could explain these seemingly divergent results? One would assume that the incidence of anemia could have been prevented through early and more frequent prenatal care. In contrast, the occurrence of pregnancy-induced hypertension or gestational diabetes may well reflect a heightened surveillance for these complications as opposed to differences in prenatal care. Previous studies of public certified nurse-midwife maternity programs have failed to explore antenatal complications. Our finding of a significantly higher proportion of induced or stimulated labor among women from the intervention group appears contrary to previous published reports suggesting that deliveries managed by certified nurse-midwives involve minimal labor induction or stimulation.'727 A partial explanation may be the difference in the obstetrical risk profile of the study populations and the institutional settings used for comparisons. In previous studies, the birth center provided the setting for low-risk deliveries by certified nurse-midwives (in contrast to hospital intrapartum care among a mixed-risk population in our study). Perhaps the hospital setting reinforces active obstetric management in childbirth. Our finding of nearly equivalent cesarean rates is puzzling in view of the expectation of lower rates among the intervention group, given the philosophical bias of certified nurse-midwives against this procedure. Two previous studies reported nonsignificant reductions in cesarean procedures.'7'28 These results reflect a potential for reducing the risk of cesarean delivery only among low-risk deliveries, which may not translate into a low-income, mixed risk obstetric population. Vaginal births after cesarean, rather than a repeat cesarean, have been advocated for women with a previous cesarean birth.29 It is therefore encouraging to note that the intervention program was successful in increasing the proportion of such births. Previous certified nurse-midwife evaluation studies have overlooked vaginal birth after cesarean as a study outcome. Our analysis indicated that infants born to mothers from the intervention county were less likely to be premature than infants from the comparison counties, and the proportion of low-weight births was reduced by 24%. Both findings were of borderline statistical significance. Previous studies among certified nursemidwife programs do not all agree with our results. In a randomized study, Slome et al. found a non-significant increase in the pro- 678 American Journal of Public Health

5 portion of low-weight births and no difference in premature infants in deliveries attended by nurse-midwives and hospital staff physicians.28 The authors found a healthier population among the physician care group, which may have biased their results. Reid and Morris reported a significant drop in the proportion of low-birthweight infants after implementation of a public certified nurse-midwife program.'3 The difference in low-weight births between previous studies and our research may be accounted for by differences in the content of prenatal care provided.30 However, we are cautious about speculating on these divergent outcomes since our analysis and other certified nurse-midwife studies did not examine content ofprenatal care. There are several limitations to our study that need to be considered. The primary source of data was birth certificates; if information on these forms was not altogether valid, this could have resulted in a bias of true associations. Studies have found that basic demographic data and birthweight are often well reported but that the accuracy of data on complications and procedures varies.3' An important caveat in interpreting the generalizability of these results is the small sample of counties used for comparisons. Our study suffered from a small sample size at the community level (n = 3 counties) and thus resulted in an increase in type II error and a reduction of statistical power. It would have further strengthened our conclusions had we had the opportunity to gather and compare data on indigent births prior to the initiation of this intervention model. Funding limitations prevented extending our analysis in this manner. Selection bias, regarded as a major pitfall among most evaluative studies of certified nurse-midwife perinatal care, may have been diminished in our analysis, which mimicked an "intention-to-treat" approach by including all eligible women regardless of whether they saw a certified nurse-midwife. This mixed-risk study population was uniformly limited to medically indigent women. Our study design was further strengthened by use of a random-effects logistic regression model to account for community-level variation. As noted, in the past, many comparison studies similar to ours neglected to account for this important source of variability.32 The results of this population-based study offer limited support for the role of a public-private certified nurse-midwife maternity program in the deliveries of medically indigent women. Increasing access to Medicaid may not, by itself, narrow the gap in matemity care between the low-income and general populations.23 33'34 By providing a continuum of care, a public-private certified nurse-midwife program might be able to reduce some of the higher risks associated with indigent births. The results of our study may be helpful to health policymakers who must address the issue of inadequate maternity care and poor birth outcomes for low-income women. D References 1. Akin BV, Rucker L, Hubbell FA, Cygan RW, Waitzkin H. Access to medical care in a medically indigent population. J Gen Intern M. 1989;4: Brazzoli GJ. Health care for the indigent: overview of critical issues. Health Serv Res. 1986;21: Davidson EC, Gibbs CE, Chapin J. The challenge of care for the poor and underserved in the United States. Am JDis Child. 1991;145: Nutter DO. Medical indigency and the public health care crisis: the need for a definitive solution. 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