Police have sealed off Reinwood Road in the Marsh area of the town and a man in his 30s has been arrested.
The 37-year-old woman was found at a house with stab wounds. The man is being held on suspicion of her murder.
A baby girl was among four children in the house at the time.
This morning police confirmed a murder inquiry had been launched.
A spokesman said officers were called to Reinwood Road at 9.32pm on Sunday after receiving calls about an “domestic related incident”.
He added: “A 37 year old woman was located inside the property who had suffered a serious stab injury. She was taken to hospital but later died.
“A nine year old boy was also found outside the property who had suffered a stab wound to his arm and was treated in hospital. Another nine year old boy, an 11 year old boy and a six month old baby girl were also present and treated for minor injuries.”
Investigating Officer, Detective Chief Ady Taylor said: “A 39 year old man was detained at the scene and is being treated in hospital today for serious injuries. We are not looking for anyone else in connection with this incident.”
Reinwood Road is expected to be closed for the rest of the day.
Anyone with information is asked to call 101 or Crimestoppers on 0800 555 111.