Task-Shifted Mental Health Counseling and Postpartum Trauma Recovery in Kenyan Maternal Clinics: A Stepped-Wedge Implementation Trial Estimating Coverage-Dependent Effectiveness

Task-shifted mental health counseling is widely promoted as a means of extending trauma care into maternal clinics in low-resource settings, yet the coverage levels at which such programmes can be expected to detect clinically meaningful improvements in postpartum trauma recovery remain poorly characterised. Using a between-cluster standard deviation of 6.0, a residual standard deviation of 4.5 and an intraclass correlation of 0.640, power was estimated across 2000 replications per design cell for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The analysis indicates that 54 clusters are required to detect a 5 percentage point improvement at 80% power, and that the minimum detectable effect declines steeply as cluster numbers rise from 8 to 32. These results imply that coverage-dependent effectiveness claims in task-shifted trauma care require cluster numbers substantially larger than those typical of published implementation trials, and that underpowered stepped-wedge designs risk misclassifying modest but clinically meaningful recovery gains as null.