We included peer-reviewed primary studies that met the following criteria: (1) Population: Preterm infants (born before 37 weeks of gestation). (2) Concept: Developmental care interventions, including but not limited to kangaroo mother care, noise/light reduction strategies, individualized developmental support, family-integrated care, and neuroprotective practices. (3) Context: Neonatal intensive care units (NICUs), step-down units, and community-based follow-up care. (4) Study Types: Quantitative (RCTs, cohort, cross-sectional), qualitative, and mixed-methods studies were included. Reviews, editorials, conference abstracts, and protocol papers were excluded. Only studies published in English between January 2020 and July 2025 were included.

A comprehensive and systematic literature search was conducted across five major electronic databases: PubMed, Scopus, CINAHL, Web of Science, and EMBASE. These databases were selected to capture a wide range of interdisciplinary studies spanning medicine, nursing, and public health. To ensure thoroughness and reduce publication bias, supplementary searches were performed through Google Scholar and manual screening of the reference lists of all included studies to identify additional relevant literature that may not have been indexed in the primary databases. The search strategy was developed in consultation with a health sciences librarian and involved a combination of controlled vocabulary (e.g., MeSH terms) and free-text keywords. The terms were iteratively tested and refined to maximize sensitivity and specificity. Key search terms included: (“preterm infant” OR “premature baby” OR “low birth weight infant”) AND (“developmental care” OR “kangaroo care” OR “neonatal individualized care” OR “family-centered care”) AND (“intervention” OR “program” OR “strategy”). Boolean operators (AND, OR), truncation symbols, and database-specific filters (e.g., language, publication year) were applied to tailor the search to each platform.

The bibliographic search was conducted between 1 July and 15 August 2025 across multiple databases. The search strategy was designed to identify recent and high-quality evidence; therefore, only peer-reviewed articles published in English between January 2020 and July 2025 were included. The search targeted titles and abstracts using predefined keywords and Boolean operators to capture studies focusing on developmental care for preterm infants. Whenever full texts were available, they were retrieved and screened in full to confirm eligibility, assess methodological quality, and extract detailed data. All search results were documented systematically, including the number of records retrieved, screened, excluded, and retained, following PRISMA-ScR guidelines. A reference management system was used to remove duplicates and maintain an auditable trail of decisions during the screening and selection process, ensuring the reproducibility and transparency of the review.

All search results were first imported into EndNote 20 for reference management, where duplicate records were systematically identified and removed. Following this, two reviewers independently screened the titles and abstracts of the remaining studies to assess their relevance according to the predefined eligibility criteria. For studies that appeared to meet the inclusion criteria or where eligibility was unclear, the full texts were retrieved for further evaluation. These full-text articles were then independently assessed by the same two reviewers to determine their final inclusion in the review. In instances where discrepancies arose between the reviewers regarding the eligibility of specific studies, consensus was achieved through discussion. If agreement could not be reached, a third reviewer was consulted to provide resolution and ensure methodological rigor.

A standardized data extraction form was developed and pilot-tested to ensure consistency and reliability in capturing relevant information across studies. Using this form, two reviewers independently extracted data from each included article. Extracted variables encompassed the following elements: author(s), year of publication, and country of origin; study objectives and methodological design; characteristics of the preterm infant population (including gestational age, birth weight, and clinical status); type and detailed description of the developmental care intervention implemented; outcome domains assessed, including neurodevelopmental, behavioral, physiological, and parental outcomes; setting and context of intervention implementation (e.g., NICU level, healthcare system characteristics, or geographic setting); and key findings, including reported effects, feasibility, and limitations of the intervention. Any discrepancies in data extraction were resolved through discussion, with input from a third reviewer when necessary to ensure accuracy and consensus.

Although quality assessment is not mandatory in scoping reviews, a structured critical appraisal was conducted to enhance the interpretability and contextual relevance of the included studies. The Mixed Methods Appraisal Tool (MMAT) 2018 version was employed to assess the methodological quality of all eligible empirical studies, encompassing randomized controlled trials (RCTs), non-randomized studies, qualitative studies, mixed-methods designs, and quantitative descriptive studies (26). Each study was first categorized according to its methodological design. Two independent reviewers (initials blinded for peer review) evaluated each study against five design-specific criteria in the MMAT. Responses were rated as “Yes,” “No,” or “Can't tell” for each criterion. Discrepancies were resolved through discussion or adjudicated by a third reviewer. The appraisal focused on internal validity, clarity of research questions, adequacy of data collection and analysis methods, and coherence between findings and conclusions. No studies were excluded based on quality scores; instead, appraisal results were used to contextualize evidence strength across themes and are summarized narratively in the results section (Supplementary Material S1).

Inter-rater agreement was calculated using Cohen's kappa coefficient to ensure consistency of ratings. Studies with lower MMAT ratings were interpreted cautiously in the synthesis phase, especially when drawing conclusions about effectiveness, feasibility, or transferability of developmental care interventions.

Extracted data were synthesized using a descriptive approach to provide an overview of the existing evidence. A combination of narrative and thematic synthesis was employed to systematically map the breadth and diversity of developmental care interventions, the associated outcome domains, and the contextual factors influencing implementation, such as geographic location, healthcare setting, and resource availability. The findings were organized to highlight patterns, similarities, and variations across studies. To enhance interpretability, the results are presented in tabular format and thematically grouped according to the type of intervention, targeted outcomes (e.g., neurodevelopmental, physiological, psychosocial), and contextual elements. This method allowed for the identification of gaps in the literature and emerging trends in the delivery of developmental care for preterm infants.

To enhance transparency in study selection, the PRISMA 2020 flow diagram was supplemented with detailed documentation of each exclusion step. An initial 2,500 records were identified across databases and registers. Prior to screening, 500 records were removed through automated and manual filtering. Automated duplicate identification using EndNote 21.2 removed 200 duplicates, while Rayyan's machine-learning relevance classifier (2024 Beta version) flagged 100 records as ineligible based on population mismatch, document type, or methodological irrelevance; all were manually confirmed before exclusion. An additional 200 records were removed for other reasons, including non-English publications (n = 72), publication dates outside the 2020–2025 range (n = 55), lack of abstracts (n = 32), non–peer-reviewed material (n = 28), and retracted publications (n = 13).

A total of 2,200 records were screened manually at title and abstract level by two independent reviewers, resulting in 2,000 exclusions due to misalignment with inclusion criteria. Full text was sought for 200 records; however, 50 articles could not be retrieved despite attempts via institutional libraries, interlibrary loans, author contact, and academic networks. All 50 abstracts were examined, and while some appeared potentially relevant, lack of methodological detail prevented reliable inclusion. Among the 150 full-text articles assessed, 115 were excluded due to irrelevance to developmental care (n = 60), different populations (n = 30), or insufficient data (n = 25). Ultimately, 35 studies met all criteria and were included in the final synthesis (Figure 1).

Studies employing randomized controlled trial (RCT) designs represented the highest methodological quality in this review. For example, Arslan et al. (15), Çaka et al. (16), Wang et al. (17), and Tiryaki et al. (21) clearly articulated randomization procedures, used control groups, and reported outcomes with minimal bias, thereby supporting strong causal inferences regarding the effectiveness of Kangaroo Mother Care (KMC) and Family Integrated Care (FICare). These trials consistently showed improvements in physiological stability, neurobehavior, and caregiver preparedness.

High-quality cluster RCTs and prospective cohort studies such as those by Murphy et al. (27) and Moe et al. (28) offered robust longitudinal data linking FICare interventions to improved breastfeeding rates, neurodevelopmental scores, and reduced hospital stay durations. These studies demonstrated adequate control for confounding variables and high follow-up retention, enhancing confidence in the reliability of their findings. Moderate-to-high quality quasi-experimental studies and mixed-methods research, including work by Chaudhari et al. (29), Kostilainen et al. (30), and McFadden et al. (31), contributed valuable evidence on the psychosocial and developmental effects of maternal-infant bonding interventions, such as maternal singing during KMC and cue-based feeding. Although these studies lacked randomization or full blinding, they employed rigorous outcome measurement tools and added contextual insights regarding intervention feasibility and acceptability.

Retrospective and non-randomized studies such as Liang et al. (32), Zahedpasha et al. (6), and Yang et al. (33) were rated as moderate quality due to design limitations, including potential selection bias and limited adjustment for confounders. Nevertheless, they offered important contributions, particularly in underrepresented settings like China and Iran, by documenting long-term effects of FICare on language development, growth, and microbiome composition. Smaller feasibility and pilot studies, including Rivera (34) and Menke et al. (7), were rated as moderate to low quality due to small sample sizes, absence of comparison groups, and short follow-up periods. However, they provided innovation-focused insights into caregiver education, music therapy, and other adjunctive developmental care modalities.

Despite the variation in design rigor, most studies clearly articulated research objectives and aligned their methods accordingly. However, consistent gaps included the underuse of implementation science frameworks, insufficient blinding, and limited long-term tracking. These findings underscore the need for more methodologically integrated developmental care research, particularly in low- and middle-income countries (20). Overall, the included studies provide a reasonably strong evidence base, with opportunities to strengthen quality through more rigorous trial designs and implementation-focused methodologies (Supplementary Material S1).

This systematic review includes 35 primary studies investigating various developmental care interventions for preterm infants. These studies collectively reflect diverse geographic regions, research designs, clinical settings, intervention modalities, and outcome domains, offering comprehensive insight into the global implementation of developmental care strategies in neonatal intensive care units (NICUs) (Table 1).

The present scoping review identified six major thematic domains in the current evidence base regarding developmental care interventions for preterm infants in NICU settings: (1) Family-Centered and Integrated Care, (2) Kangaroo Mother Care (KMC), (3) Cue-Based and Individualized Developmental Care, (4) Environmental Optimization, (5) Multisensory and Psychosocial Interventions, and (6) Contextual and Implementation Factors (Table 2).

Despite the growing body of evidence supporting developmental care interventions for preterm infants, several critical gaps remain evident across the literature. One prominent limitation is the fragmented nature of existing research, with most studies evaluating singular interventions such as kangaroo mother care (KMC) or family integrated care (FICare), rather than assessing the synergistic potential of multi-component or systems-based developmental care models (12, 21, 27). This narrow focus restricts understanding of how these approaches interact and complement each other in real-world clinical settings. Furthermore, there is substantial heterogeneity in the outcomes measured and the tools used across studies. While some employed standardized neurodevelopmental assessments like the Bayley Scales (32), others relied on observational checklists or institution-specific indicators, complicating efforts to synthesize findings and conduct meta-analyses.

Another critical gap lies in the geographic distribution of research. A majority of studies were conducted in high-income countries, particularly Canada, Turkey, and the Netherlands, with relatively few rigorous studies emerging from low- and middle-income countries (LMICs), despite the disproportionate burden of preterm births in these settings (13, 29, 48). The underrepresentation of LMIC contexts limits the global applicability of findings and raises questions about the feasibility of implementing certain interventions in resource-constrained environments. Compounding this issue is the scarcity of studies incorporating long-term follow-up beyond the neonatal period. Although a few longitudinal evaluations have demonstrated sustained benefits of interventions like NIDCAP and FICare on motor and cognitive outcomes into early childhood (18), most studies concluded at NICU discharge or within the first year of life, leaving the extended developmental trajectory largely unexplored.

A notable limitation of the current evidence base is the limited use of established implementation science frameworks to examine how developmental care interventions are adopted, integrated, and sustained within real-world NICU environments. Many of the included studies focused primarily on clinical outcomes without systematically evaluating critical implementation domains such as caregiver readiness, staff training requirements, organizational culture, cultural acceptability, and infrastructure constraints (20). These factors play a central role in determining whether an intervention that is effective under controlled conditions can be successfully scaled or embedded into routine practice. The absence of such analyses risks overlooking how interventions interact with the complexity of NICU workflows, multidisciplinary teams, and resource variability, particularly in low- and middle-income countries (LMICs).

Addressing these gaps requires a deliberate shift toward systems-oriented research designs that conceptualize developmental care as an integrated framework rather than as discrete practices. Future studies should systematically apply implementation science models such as the Consolidated Framework for Implementation Research (CFIR) or RE-AIM to assess feasibility, fidelity, contextual barriers, and sustainability over time. Mixed-methods and longitudinal designs are essential for capturing both clinical outcomes and implementation processes, including caregiver engagement, health worker adoption, and contextual adaptations (34). Applying CFIR would allow researchers to map how developmental care components interact with organizational culture, staffing models, caregiver readiness, and contextual constraints within NICUs. Likewise, the RE-AIM framework (Reach, Effectiveness, Adoption, Implementation, Maintenance) offers a structured lens for assessing how well developmental care interventions penetrate diverse populations, achieve clinical and developmental outcomes, and sustain their impact over time. Additionally, the i-PARIHS framework (integrated-Promoting Action on Research Implementation in Health Services) can guide evaluations of facilitation strategies and context-specific adaptations, which are vital in LMIC NICU settings where infrastructural and cultural variability may influence program uptake.

In addition, establishing core outcome sets and standardized tools would improve consistency and comparability across studies, enabling stronger cross-study inferences. Targeted investment is also needed to advance developmental care research in LMICs through community-engaged, culturally sensitive approaches that account for resource limitations and sociocultural norms. Emerging digital innovations, such as mobile health applications, tele-coaching platforms, and remote monitoring tools offer promising pathways for scaling interventions equitably. Evidence from early studies integrating these technologies within Kangaroo Mother Care (KMC) and Family Integrated Care (FICare) models demonstrates improvements in caregiver engagement, knowledge retention, and continuity of care. Expanding these technology-enabled strategies could enhance global access to developmental care and strengthen neonatal outcomes across diverse settings.

Several limitations should be acknowledged in interpreting the findings of this review. First, although the search strategy was comprehensive and covered multiple databases, the review was restricted to studies published in English. This language restriction may have excluded relevant research from non-English-speaking regions, including low- and middle-income countries (LMICs), where innovative developmental care practices may be reported in local languages. Second, the substantial heterogeneity across the included studies—in terms of methodological design, intervention modalities, outcome measures, follow-up periods, and contextual factors—precluded the possibility of conducting a meta-analysis or performing direct quantitative comparisons. Consequently, the ability to draw robust generalizable estimates of effect is limited. Third, although both quantitative and qualitative evidence was incorporated, methodological quality varied considerably, particularly among observational and quasi-experimental studies, potentially influencing the strength and reliability of the conclusions. Fourth, publication bias remains a possibility; studies with positive or statistically significant findings are more likely to be published, and grey literature, conference proceedings, and non-indexed sources were not systematically screened. Lastly, while this review aimed to explore contextual and implementation-related dimensions of developmental care, reporting on these aspects was often limited or insufficiently detailed in the included studies, thereby constraining the depth of synthesis that could be achieved using implementation science or health systems frameworks.