Table 1. Summary of analysis boundaries.

Issues for consideration	Approach chosen	Justification of choice
Objectives of analysis	Cost analysis: to calculate total financial and economic costs and cost-efficiency of the intervention.Cost-effectiveness analysis: to calculate cost per improvement in coprimary outcomes (maternal perinatal depression at 12 months postnatal and child cognitive development at 24 months of age) and to compare costs to a vector of benefits, including indicative estimates of long-term gains, such as improved education outcomes and increased income in adulthood.	These are the most feasible objectives for analysis, given the time and resource constraints.
Audience	Researchers, healthcare workers and policy makers	Health economic evaluation commissioned by trial team.
Viewpoint	Societal perspective	Useful to multiple stakeholders to determine appropriate resource allocation.
Time
a)Time of the intervention	April 2018 to December 2023	As per updated RCT protocol, with delays in measuring coprimary outcomes due to the COVID-19 pandemic.
b)Time over which benefits experienced	Approximately third trimester until 24 months post partum.	Benefits should be realised from the start of therapy (third trimester) until the final coprimary outcomes are measured at 24 months post partum.
Analytical horizon	The outcomes time horizon will run from when the first coprimary outcomes are measured (2019) until the final coprimary outcomes are measured (2024), that is, 5 years.The costing time horizon will run from inception (2016) until all therapy sessions are completed (2023), that is, 8 years.	The benefits time horizon will be updated to ensure that it matches the costs time horizon.
Which alternatives could be used for comparison?	Enhanced standard of care (ESoC)	ESoC provided to participants in the control arm of the trial.
Target population(s)	Pregnant women who are diagnosed HIV-positive; aged 16 years and above (all participants were above 18); meet the criteria for antenatal depression as defined by a score of ≥9 on the Edinburgh Postnatal Depression Scale; live or are planning to live within the study area at the time of delivery and for at least 9 months after delivery (intensive therapy period); are conversant in isiZulu or English. Exclusion criteria may be found in Rochat et alhere. in Rochat et al..1	HIV-positive women have a higher risk of developing perinatal depression and they and their infants suffer from worse consequences thereof.
Coverage	To be implemented at 88% (15/17) of clinics in the district.	These clinics are research sites for a research centre.
Type of analysis	Cost-effectiveness analysis	Cost and consequences data are collected for the interventions and comparator.

RCTrandomised controlled trial