Man charged after Sydney woman's death

The boyfriend of a young woman found dead at a Sydney home has been charged with contravening an apprehended domestic violence order.

Hayley Mcclenahan-Ernst, who was reportedly pregnant, died at a Kingswood home despite efforts from paramedics on Sunday.

Police say they were called to the home shortly after midnight.

The 21-year-old's death is being treated as suspicious, and Task Force Fielding has been set up to investigate.

"Can not believe the news I just received," Christine Jutta Chaffey posted on Facebook.

"An amazing beautiful... friend has passed away too soon."

Superintendent Greg Peters on Sunday said it was thought the woman and the 21-year-old man were in a relationship but that he didn't know if they lived together.

He would not say if the young woman had suffered any injuries and told reporters a post-mortem examination would hopefully be performed on Monday.

"We don't know what's caused the death," he said.

"There were a number of people in the house at the time and they are assisting us with our inquiries."

The man was charged after being questioned at St Mary's police station.

He was refused bail and is due to appear in Penrith Local Court on Monday.