The normal value of neonatal jaundice is not a fixed value, but an approximate range, and it varies in standard for babies born at different months of age. If a full-term baby is born with a serum bilirubin value of less than 221 μmol/(12.9 mg/dl), this is the normal range. Jaundice appears in full-term babies on the 2nd-3rd days after birth, and is heaviest on the 4th-5th days, and usually disappears within 2 weeks of birth. In contrast, preterm babies have their serum bilirubin values measured to be less than 257 μmol/L (15 mg/dl), which is the normal range. Their jaundice mostly occurs on the 3rd-5th day after birth, peaks on the 5th-7th day, and can subside on the 7th-9th day, and the longest can be delayed to subside after 3-4 weeks, which all belong to is physiological jaundice.