Community Mental Health Service Contraceptive Co-Provision and Unplanned Pregnancy Risk Among Women With Severe Mental Illness in South African Districts: A Target-Trial Emulation

Women with severe mental illness in South African districts face elevated unplanned pregnancy risk, yet community mental health services rarely co-provide contraception. No observational data are used or claimed. Under a declared variance structure with between-cluster standard deviation 6.0, residual standard deviation 4.5 and intraclass correlation 0.64, power was estimated across 2000 design cells spanning 8, 16, 24 and 32 clusters and effects of 3, 5 and 8 percentage points. The analysis identifies 54 clusters as the number required for 80% power at a 5-percentage-point effect, a figure that exceeds the district counts typically available to South African community mental health evaluations. Minimum detectable effect curves show that at 8 clusters only effects of roughly 8 percentage points are reliably detectable, while at 32 clusters the detectable effect falls to approximately 5 percentage points. The framework reframes contraceptive co-provision as a co-located service-modification question rather than a contraceptive-demand question, and specifies the design conditions under which South African districts can generate credible evidence.