NSW Police called hours before woman fatally stabbed at St Marys in Western Sydney
The partner of a woman who was stabbed to death in her Western Sydney home has been charged with murder, while an internal police investigation examining an earlier welfare call is underway. 
The welfare call was made just hours before mother-of-four Drew Douglas, aged in her 30s, was stabbed in the chest and died at her St Marys home on Wednesday morning.
Her partner was arrested and had been assisting police with their investigations before he was later charged in the evening.
At 8:40pm on Tuesday, police received a call from Ms Douglas's partner, who was concerned about his own mental health.
There were no threats of violence made during the call and officers did not attend the address.
At 6:45am today, a triple-0 call was made by Ms Douglas at the property about a stabbing.
Police attended the property at Edmondson Avenue and found Ms Douglas with stab wounds to her chest.
Officers performed CPR and paramedics arrived shortly afterwards to continue medical treatment but she died at the scene.
At 7:30am, the woman's partner drove himself to Campbelltown police station where he was later arrested.
Police have launched a critical incident investigation into the circumstances surrounding Ms Douglas's death.
Assistant Commissioner Leanne McCusker said the investigation would examine why police did not attend the house last night after the welfare call.
"The nature and further detail of that call will be subject to the critical incident investigation," she said.
Ryde Police Area Command will lead the investigation and closely examine the timeline of events and whether police had an opportunity to intervene last night.
Assistant Commissioner McCusker said the couple had a history of domestic violence but there were no pending charges or apprehended violence orders in place.
The couple's children are now receiving support from police and other government agencies.
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