Why do newborns have physiological jaundice?

Jaundice is characterized by yellowing of the skin and yellowing of the sclera (commonly known as the whites of the eyes). In general, jaundice indicates the existence of a disease, so why is it called physiological jaundice?

Physiological jaundice occurs at a specific age and under certain circumstances, that is, within the first 2~10 days of life. Jaundice appears in full-term newborns about 2~3 days after birth, and jaundice is most obvious at 4~6 days, and most of them resolve within 7~10 days after birth. If yesprematureJaundice can subside as late as the 2~3 weeks after birth.At the stage of jaundice, the newborn is generally well, such as loud crying, strong sucking of breast milk, free movement of limbs, and yellow stools. If blood is drawn for bilirubin, the value does not exceed 205.2 micromoles/liter.

If the occurrence of jaundice does not meet the above conditions, it cannot be called physiological jaundice, and jaundice may be caused by the disease, and you should go to the hospital for further examination in time.

In the womb, the oxygen in the mother's blood diffuses to the red blood cells of the fetus, and then carries oxygen to all parts of the fetal body, so the red blood cell value in the fetal blood is as high as (6~7)×1012/L [The average child is (4~5)×1012/L]o When the fetus is delivered and leaves the mother for spontaneous breathing, it does not need so many red blood cells.

In addition, the lifespan of red blood cells in the fetus is relatively short, so a large number of red blood cells are destroyed, and bilirubin, a metabolite of red blood cells, accumulates in large quantities.Bilirubin has to be "processed" by the liver, and the liver function of newborns is poor, and there is a phenomenon of "too many raw materials and insufficient processing capacity" in the factory, and the excess of free bilirubin shows jaundice. With the increase of age and the maturity of liver function, bilirubin is gradually "processed" by the liver, and jaundice gradually decreases and finally resolves.