An unborn child has no blood production
from itself but uses the blood of the
mother, which is transported by the
umbilical cord. Immediately after birth the
own blood production of the child will
develop and the blood of the mother will
gradually be broken down and replaced
by the child its own blood. The waste that
remains from the (prenatal) blood is
bilirubin (formerly referred to as
hematoidin) which normally will be
excreted by the liver. In some occasions,
especially with children who were born
(too) early, the liver is not yet able to deliver the necessary break down capacity and
the surplus of bilirubin will accumulate in the bloodstream, leading to neonatal jaundice
which makes the skin of the child look yellow. Radiating the skin with blue light with a
wavelength of 458 nanometers would break apart the bilirubin and the yellow tint
would disappear. Since other and more severe diseases also might cause a yellow
tinted skin, treatment of a newborn baby with blue light was only allowed to be
performed by- or under the supervision of a physician.