Doctors in Japan have successfully transplanted liver cells derived from embryonic stem cells into a newborn baby, in a world first that could provide new treatment options for infants.

The newborn was suffering from urea cycle disorder, where the liver is not capable of breaking down toxic ammonia.

But the six-day-old was too small to undergo a liver transplant, generally not considered safe until a child weighs around six kilograms at around three to five months old.

Doctors at the National Center for Child Health and Development decided to try a "bridge treatment" until the baby was big enough, injecting 190 million liver cells derived from embryonic stem cells (ES cells) into the blood vessels of the baby's liver.

Following the treatment, "the patient did not see an increase in blood ammonia concentration and was able to successfully complete the next treatment", namely a liver transplant, the institute said in a press release.

The baby, whose sex has not been disclosed, received a liver transplant from its father and was discharged from the hospital six months after birth.