To compare the course of the transcutaneous bilirubin (TcB) values of early-term newborns with those of term newborns in the first month of life and to investigate whether early-term newborns have an increased risk of significant hyperbilirubinemia requiring treatment. A prospective, controlled cohort analysis. A tertiary level mother-child birth and health care center. Four hundred early-term (37 0/7 to 38 6/7 weeks) and 320 term (39 0/7 to 41 6/7 weeks) newborns born during a 27-month period. A total of six TcB measurements in a longitudinal manner were made in early-term and term newborns: the first two at 6 and 48 hours after birth and the next four on routine examination days (Days 4, 7, 15, and 30). Demographic characteristics, values of daily TcB measurements, number of newborns with significant hyperbilirubinemia, and risk of jaundice requiring treatment were compared between the two groups. All six TcB values were significantly greater in the early-term group than in the term group (p < .001 for each). Early-term newborns had a statistically significant increased risk of jaundice requiring treatment compared to term newborns (risk ratio = 1.91; 95% confidence interval [1.23-2.96]; p = .0046). Results of the repeated-measures analysis of variance and post hoc adjusted multiple comparison analysis showed that TcB levels increased to and peaked at 96 hours after birth and then gradually decreased to baseline (first measurement) levels at 30 days after birth in each group. Early-term newborns should not be treated as full-term newborns because they have significantly higher TcB levels. These newborns should be closely monitored for pathologic jaundice because they have increased risk for significant hyperbilirubinemia requiring phototherapy.