Antenatal care trial interventions: a systematic scoping review and taxonomy development of care models

Abstract

Background: Antenatal care models vary widely around the world, reflecting local contexts, drivers and resources.
Randomised controlled trials (RCTs) have tested the impact of multi-component antenatal care interventions on
service delivery and outcomes in many countries since the 1980s. Some have applied entirely new schemes, while
others have modified existing care delivery approaches. Systematic reviews (SRs) indicate that some specific antenatal
interventions are more effective than others; however the causal mechanisms leading to better outcomes are poorly
understood, limiting implementation and future research. As a first step in identifying what might be making the
difference we conducted a scoping review of interventions tested in RCTs in order to establish a taxonomy of antenatal
care models.
Methods: A protocol-driven systematic search was undertaken of databases for RCTs and SRs reporting antenatal care
interventions. Results were unrestricted by time or locality, but limited to English language. Key characteristics of both
experimental and control interventions in the included trials were mapped using SPIO (Study design; Population;
Intervention; Outcomes) criteria and the intervention and principal outcome measures were described. Commonalities and
differences between the components that were being tested in each study were identified by consensus, resulting in a
comprehensive description of emergent models for antenatal care interventions.
Results: Of 13,050 articles retrieved, we identified 153 eligible articles including 130 RCTs in 34 countries. The interventions
tested in these trials varied from the number of visits to the location of care provision, and from the content of care to the
professional/lay group providing that care. In most studies neither intervention nor control arm was well described. Our
analysis of the identified trials of antenatal care interventions produced the following taxonomy: Universal provision model
(for all women irrespective of health state or complications); Restricted ‘lower-risk’-based provision model (midwifery-led or
reduced/flexible visit approach for healthy women); Augmented provision model (antenatal care as in Universal provision
above but augmented by clinical, educational or behavioural intervention); Targeted ‘higher-risk’-based provision model
(for woman with defined clinical or socio-demographic risk factors). The first category was most commonly tested in
low-income countries (i.e. resource-poor settings), particularly in Asia. The other categories were tested around the world.
The trials included a range of care providers, including midwives, nurses, doctors, and lay workers.
Conclusions: Interventions can be defined and described in many ways. The intended antenatal care population group
proved the simplest and most clinically relevant way of distinguishing trials which might otherwise be categorised
together. Since our review excluded non-trial interventions, the taxonomy does not represent antenatal care provision
worldwide. It offers a stable and reproducible approach to describing the purpose and content of models of antenatal
care which have been tested in a trial. It highlights a lack of reported detail of trial interventions and usual care processes.
It provides a baseline for future work to examine and test the salient characteristics of the most effective models, and
could also help decision-makers and service planners in planning implementation.