RESUMEN
The South Asian region, including Pakistan, reports one of the highest rates of perinatal depression. Effective task-shifting perinatal mental health interventions exist and are gaining attention of policy makers, as a potential solution to bridge the existing treatment gap. However, no specific indicators are available to gauge the level of implementation for such interventions in the South Asian region. The Thinking Healthy Programme Peer-delivered (THPP) is a perinatal mental health intervention delivered, at scale, by peer volunteers (PVs). An effectiveness trial for THPP based on 570 depressed pregnant women was conducted in rural Rawalpindi, Pakistan. In addition, we also examined the implementation processes of THPP in order to develop an index to gauge implementation strength of this intervention. The key components of this index are based on four important intervention processes related to service provision which include; i) the competence of PVs, ii) supervisions attended by PVs and iii) number and iv) duration of THPP sessions. We attempt to inform an implementation strength index which best correlates with reduced perinatal depression and disability at 6 months post childbirth. Knowledge of such an implementation strength index for a task-shifted perinatal depression intervention carries implications for scale up strategies.