BackgroundSimple, low-cost anthropometric screening tools like foot length (FL) can be used to screen for small babies (low birth weight (LBW) or preterm) delivered at home or in facilities where functional weighing scales are unavailable. This study aimed to evaluate the accuracy and utility of newborn FL screening tools to help identify small babies by mothers.MethodsA mixed-method study was conducted at selected health facilities from 15 May to 6 July 2024. The consecutive sample included 396 mother-newborn dyads. Mothers screened newborns using laminated cards and plastic tools with colour codes (green/red) based on a 73 mm FL cut-off. In-depth interviews were also conducted with purposively selected participating mothers. The screening tools' diagnostic accuracy was evaluated by receiver operating characteristic curve analyses.ResultsThe mean maternal age was 26.9 years. There were 61 (15.4%) LBW and 48 (12.3%) preterm babies. Using the laminated card, mothers classified 39.4% of newborns as having a short foot, while 33.1% were classified as such using the plastic tool. The plastic tool showed LBW identification accuracy of 0.82 area under receiver operating characteristic curve (AUC): 0.82 (95% CI 0.77 to 0.87) compared with the laminated card AUC: 0.75 (95% CI 0.69 to 0.81). For preterm identification, both tools performed similarly (AUC: 0.73-0.74). Compared with the laminated card (81.9% sensitivity and 68.4% specificity), the plastic tool (86.9% sensitivity and 76.7% specificity) would miss fewer LBW babies and reduce unnecessary referrals. The qualitative findings also suggested that a smooth surface, footprint picture, colour codes and heel holder can increase acceptability and utilisation of the FL screening tools.ConclusionFL screening tools made from plastic or card with colour codes can be used by mothers to help identify LBW and preterm babies. Area-specific cut-off points, a smooth surface with a footprint picture and a heel holder, should be considered while designing colour-coded FL screening tools.