We recruit pregnant women at the last trimester of pregnancy and follow the infant–mother dyads until the child is 12 months old (figure 5). We selected the first 12 months of life because it is a critical development window,81–83 (link) it is a time when children are most at risk of acute and chronic effects of enteropathogen infection84 (link) and it is a short enough period of time to avoid changes in water access that might occur. We recruit mothers at the end of their pregnancy so we can collect data on household risk factors (including drinking water quality) during the gestational period. Active recruitment occurs through identification of pregnant women in the 2020 population-based survey, lists of pregnant women visiting local health centres for prenatal care and study staff visiting under-enrolled sub-neighbourhoods throughout the recruitment period. Based on Ministry of Health data for Sofala Province (where Beira is located), virtually all mothers attend prenatal clinical visits.85 Passive strategies include referrals of pregnant women by study participants and community leaders. We aim to have complete data on a total of 548 infant–mother dyads, approximately evenly divided between the intervention and control groups. We will continue to enrol dyads into both arms until we reach a minimum of 274 dyads with complete data in each arm, to ensure temporal balance throughout the duration of the study period.
During an initial pre-birth visit, pregnant women are assessed for study eligibility: (1) 18 years or older, (2) in third trimester of pregnancy, (3) resides in enrolled study cluster, (4) not planning to move within the next 12 months, (5) carrying a singleton birth and (6) consents to take part in the study. We will reassess study eligibility at each follow-up visit and record if enrolled participants have been lost to follow-up.