Johannesburg - Limpopo police arrested a 19-year-old boy on Tuesday, in connection with murder, assault and arson in Masemola outside Lebowakgomo.
Spokesperson Colonel Moatshe Ngoepe said the teenager allegedly went to his girlfriend's house for a visit at around midnight.
"On arrival, a conflict ensued between the couple until the suspect stabbed the woman with a sharp object and thereafter set the girlfriend's family house alight before he fled the scene," Ngoepe said.
"The victim and her mother managed to escape the blaze but the couple's two-month-old baby was burned to death. The victim is admitted at the hospital for medical treatment with serious stab wounds. The suspect was arrested and he will appear before the local magistrate's court soon."
Limpopo police commissioner Lieutenant General Nneke Ledwaba condemned domestic-related incidents and said they were still prevalent in some areas of the province.
The provincial police urged community members to consult with local professionals for intervention when they are having domestic-related problems.