Co-authors affiliated with HARC's coordinating center conceptualized and designed the observational study, gathered and analyzed data, interpreted study results, and drafted and revised this manuscript. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for reporting observational studies22 was used to ensure rigorous reporting of the study (see additional information). National model leadership identified staff to take the lead as their representatives and co-authors for this study. Co-authors representing home visiting models provided study data, interpreted results, and revised the manuscript. Figure 2 illustrates how sample selection and data collection mapped to the Precision Paradigm.
Selection of Home Visiting Models
The intended sample was evidence-based models enrolling families prenatally to promote healthy birth outcomes. We identified models meeting three criteria: designated as evidence-based by the Home Visiting Evidence of Effectiveness (HomVEE) review; implemented in states or tribal communities in the United States; and enrolling families prenatally. Eight models met these criteria. We contacted each model's national office to ascertain whether the model aimed to prevent premature birth or low birth weight, defined as a birth <37 weeks gestation and a birth weight <2500 grams. Two of the eight models indicated that promoting healthy birth outcomes was not a central focus. The other six models indicated that improving birth outcomes was one of their intended outcomes. Five agreed to participate in the project: Family Spirit, Kentucky’s Health Access Nurturing Development Services (HANDS), Healthy Families America, Minding the Baby, Nurse-Family Partnership, and Parents as Teachers. State administrators for the sixth model, HANDS, declined due to demands of the COVID-19 pandemic.
Model representatives three surveys mapped to the Precision Paradigm (Figure 2). The surveys worked backward, from ascertaining the risks the model aimed to reduce, to the maternal behaviors it aimed to promote to reduce those risks, to the techniques it endorsed visitors to use to promote those behaviors and the emphasis to give to each.
HARC coordinating center investigators distributed each survey to model representatives at the same time, for independent completion within 2-3 weeks. Surveys 2 and 3 were distributed after all models had completed the preceding survey. HARC coordinating center investigators encouraged model representatives to ask for clarification if they were uncertain how to answer a question. Model representatives submitted seven questions. HARC investigators emailed responses to all five models by the next working day.
Survey 1 - Intended Pathways: HARC investigators drew from the literature23, 24, 25, 26, 27 and from relevant American College of Obstetrics and Gynecologists Committee Opinions28 to identify modifiable risks for low birth weight and premature birth, and target behaviors to reduce these risks.
To minimize respondent burden, Part 1 of Survey 1 was limited to ten common, diverse, modifiable, evidence-based risk factors that could be reduced through home visiting and that fell within the scope of the current pregnancy. The risks fell into four groups: 1) health care use (inadequate prenatal care); 2) psychosocial well-being (high stress, depression, intimate partner violence); 3) behavioral health (tobacco use, alcohol use, illicit drug use); and 4) biologic risk factors (infection, diabetes, high blood pressure). The survey asked representatives to rate the priority their model gave to reducing each risk. Response choices were: not a priority, low priority, moderate priority, high priority, and not sure. A priority risk was defined as one whose reduction was designated as a low, moderate, or high priority.
Part 2 of the survey focused on 14 behaviors that could be promoted within home visiting for the current pregnancy. The behaviors fell into four groups: 1) basic health promotion (physical activity, healthy diet, stress reduction activities, social supports); 2) health care use (adherence to prenatal care visit schedule, engagement in substance use treatment, and alerting the prenatal care provider to warning signs; 3) behavioral health (stopping or reducing tobacco use, stopping or reducing alcohol use, stopping or reducing illicit drug use); and 4) specific risk reduction behaviors (condom use, developing a domestic violence safety plan, medication adherence, self-monitoring of physiologic indicators). The survey asked representatives to rate their models' expectations of home visitors for promoting specific maternal behaviors to reduce each of its priority risks. Response choices were required, recommended but not required, no expectation but compatible with our model, not compatible with our model, and not sure. A target behavior was defined as a behavior the model either required or recommended visitors to promote.
The ten risks and 14 behaviors together defined 41 unique pathways to good birth outcomes (Table 1). The literature recommended some behaviors as a way reduce multiple risks. For example, physical activity is a behavior to reduce high stress, depression, high blood pressure and diabetes. Of note, the literature characterized three risk factors -- tobacco use, alcohol use and inadequate prenatal care -- not only as risk factors but as behaviors influencing other risk factors. In the same way, we defined these three constructs as both risk factors and maternal behaviors.
At the end of Survey 1, HARC coordinating center investigators used each model's priority risks and target behaviors to define its intended pathways to good birth outcomes. An intended pathway for a model is one linking a target behavior with a priority risk. Each model could have up to 41 intended pathways; the number and nature of intended pathways depended on the model's priority risks and target behaviors to reduce those risks.
Survey 2 - Endorsement of Intervention Technique Categories in Intended Pathways: Survey 2 asked respondents to rate their models' stance regarding home visitors' use of each of 23 technique categories for each of its intended pathways. Response choices were required, recommended but not required, no expectation but compatible with our model, not compatible with our model, and not sure. An endorsed technique category was defined as one that the model required or recommended visitors to use for a specific intended pathway.
The Appendix describes the 23 technique categories. HARC coordinating center investigators defined them by adapting an existing taxonomy of behavior change techniques and by adding techniques commonly used in home visiting but not represented in the existing taxonomy. The existing taxonomy contained 93 techniques grouped into 16 categories.16 We used techniques categories rather than individual techniques to reduce respondent burden. We modified these categories in four ways: 1) split four of the original categories into eight narrower, more homogeneous categories; 2) dropped one of the original categories but assigned some of its techniques to another existing category; 3) added the category, "assess readiness for change," because it is concordant with a family-centered approach and with theories of behavior change that differentiate motivating, enabling, and reinforcing target behaviors;29 and 4) added three categories aligned with the framework of West et al.30 to reflect home visiting's use of referral and coordination.
Survey 3 - Emphasis in Using Endorsed Technique Categories: Survey 3 explored how much models expected home visitors to emphasize technique categories within and across intended pathways. To minimize respondent burden while maximizing the number of comparisons that could be made, the survey focused on 20 pathways defined by four behaviors associated with four to six different risks and designated as target behaviors by all five models.
For each model, Survey 3 was limited to the model's intended pathways and the technique categories it had endorsed for those pathways. For each intended pathway, model representatives rated the relative emphasis their model expected visitors to give to each endorsed technique category. Response choices were adapted from those of Smith et al31 and ranged from one (low emphasis) to five (high emphasis) and no stance. Response choices two through four were not labeled. A technique category with a rating of five was defined as a high-emphasis technique category.
HARC coordinating center investigators carried out data analyses. After all surveys had been completed, they shared results with model representatives in several iterations, using representatives' feedback to guide new analyses and to improve the clarity and usefulness of results.
Priority Risks, Target Behaviors and Intended Pathways: We described the distribution of model responses for each risk. We determined and graphed the number of models designating each of Table 1's 41 pathways as an intended pathway.
Stance on Technique Categories: We calculated the distribution of each model's responses (required, recommended, no expectation but compatible, not compatible, and not sure) for each technique category across all of its intended pathways combined. For all models combined, we calculated the means of the model-specific distribution of responses. We calculated the number of models designating each technique category as a high-emphasis technique category within each intended pathway.
Overview and Comparison of Models' Priority Risks, Intended Pathways, and Stance on Technique Categories: For each model, we calculated the number of priority risks, the number of target behaviors, and the number of intended pathways.
For each model, across all its intended pathways, we calculated the mean number of technique categories the model required, recommended, endorsed (the sum of required and recommended), not endorsed but compatible, and rated as not compatible with the model. To describe variability within models, we calculated the standard deviation of the number of technique categories endorsed, not endorsed but compatible, and not compatible among its intended pathways.
We explored within-model consistency in endorsement of technique categories across intended pathways with the same priority risk but different target behaviors and across intended pathways with the same target behavior but different priority risks. We used three indicators of consistency: 1) same set of endorsed technique categories; 2) same set of high-emphasis technique categories; and 3) same pattern of emphasis across of technique categories. For each model, we calculated the percentage of intended pathways in which the indicator was present.
Discussion and Interpretation of Results
HARC coordinating center investigators prepared results tables and talking points for three rounds of independent review and written feedback by model representatives followed by group discussion of the collated feedback.