OBJECTIVE: The purpose of this study was to determine the levels of Cystatin C in healthy term newborns in the first month of life. INTRODUCTION: Cystatin C may be a suitable marker for determining the glomerular filtration rate because it is not affected by maternal renal function. METHODS: Cohort study. Inclusion: term newborns with appropriate weight; mother without renal failure or drugs that could affect fetal glomerular filtration rate. Exclusion: malformations; hypertension or any condition that could affect glomerular filtration rate. Cystatin C (mg/L) and creatinine (mg/dl) were determined in the mother (Mo) and in the newborn at birth (Day‐0), 3rd (Day‐3), 7th(Day‐7) and 28th(Day‐28) days. Statistics: one way ANOVA and Pearson's correlation tests. Sample size of 20 subjects for α = 5% and a power test = 80% (p<0.05). RESULTS: Data from 21 newborns were obtained (mean ± standard deviation): MoCystatin C = 1.00±0.20; Day‐0 Cystatin C 1.70±0.26; Day‐3 Cystatin C = 1.51±0.20; Day‐7 Cystatin C = 1.54±0.10; Day‐28 Cystatin C = 1.51±0.10. MoCystatin C was smaller than Day‐0 Cystatin C (p<0.001), while MoCreatinine was not different from Day‐0 Creatinine. Cystatin C only decreased from Day‐0 to Day‐3 (p = 0.004) but newborns Creatinine decreased along the time. Correlations were obtained between MoCystatin C and MoCreatinine (p = 0.012), as well as Day‐3 (p = 0.047) and Day‐28 (p = 0.022) Cystatin C and Creatinine values. CONCLUSION: Neonatal Cystatin C values were not affected by MoCystatin C and became stable from the 3rd day of life.