Factors associated with stunting and underweight indices among children 0–3 years in Nairobi, Kenya: a cross-sectional study

Background Child undernutrition remains one of the most pressing global public health challenges, particularly in low and middle-income countries (LMICs). Most studies focus broadly on children under five, potentially overlooking the unique vulnerabilities affecting children in the first 1,000 days of life. This study investigated potential factors associated with stunting and underweight malnutritional presentation among children aged 0–3 years in Nairobi City County, Kenya. Methods We conducted a cross-sectional study of 2903 caregiver-child dyads living in Nairobi City County to assess stunting [Height-for-Age Z -scores (HAZ)] and underweight [Weight-for-Age Z -scores (WAZ)] using the World Health Organisation (WHO) growth standards among 0–3-year-olds. Child, caregiver, and household characteristics were included in the linear mixed effects regression models of factors associated with the study outcomes. Results The mean (standard deviation) HAZ and WAZ were −0.90 (1.5) and −0.38 (1.3), respectively. Approximately 22.0% of children in the study were stunted and 10.0% underweight (< −2 Z -score). Common factors associated with stunting and underweight in multivariable models were older age (β = −0.04 and β = −0.01, respectively, both p < 0.001), male gender (β = −0.30 and β = −0.22; Reference = Female, respectively, both p < 0.001), low birth weight (β = −1.19 and β = −0.94), respectively, both p < 0.001, and living in informal settlements (β = −0.15, p = 0.010 and β = −0.14, p = 0.008). Additionally, severe household food insecurity (β = −0.47, p = 0.004; Reference = Secure) was associated with stunting, while high wealth index (β = 0.16, p = 0.018; Ref = Low wealth index) and history of hospitalization (β = −0.17, p = 0.032) were associated with underweight. Conclusion The high burden of stunting and underweight in this setting signals a serious public health risk and necessitates tailored interventions targeting individual and household-level vulnerabilities.