Police say a 23-year-old Sioux Falls woman who was about to deliver a baby was at a hospital with her boyfriend when her husband showed up and pulled a knife.

Information Officer Sam Clemens says it happened around 9:40pm Tuesday at Avera McKennan Hospital.

Clemens says the boyfriend's brother and his girlfriend were also in the room when the pregnant woman's husband showed up with their two-year-old child.

Clemens says the husband let the two-year-old go into the room, then pulled a knife and went after his wife's boyfriend.

The victim and his brother took the knife away and held the man until police arrived.

Clemens says 24-year-old Stephen Michael Douglas Smith of Sioux Falls was arrested for aggravated assault and aggravated assault-domestic.

The woman's 24-year-old boyfriend had a cut to his hand that Clemens says was not serious.