Dr. Lizzy Tabane, the boy's pediatrician, said Friday that nothing can be done to save him from the condition known as anencephaly.
She said, "It's a condition not compatible with life. I do not know how long the baby will hold," but the parents are hopeful.
Baby Mokoena was born on July 4 and is being monitored at a hospital in the central Free State province of South Africa.
Tabane says that babies born with anencephaly do not usually survive long. Two of her previous cases did not live beyond two weeks.
Tabane says of the main causes of the condition is vitamin and folic acid deficiencies in pregnancy.