Figure 1.

Environmental health theory of change for HAPIN intervention. HAPIN theory of change, outlining intervention components and metrics of fidelity and adherence thought to underlie exposure and primary health outcomes. Yellow boxes represent aspects of the HAPIN trial under investigation in this paper, for the period from enrollment through to the end of gestation (relevant to the first primary outcome: newborn birth weight). Grey boxes represent outcomes further on the change pathway (not reported here). The black outline encircles this manuscript’s areas of focus. PM_2.5, particulate matter less than 2.5 μm in diameter. CO, carbon monoxide. BC, black carbon.