A baby has been found dead at a house in Sydney's west.

Emergency services found the nine-month-old child "unresponsive" after being called to a home in Doonside at 10am, NSW Police, said.

NSW Ambulance paramedics couldn't revive the child.

Police are speaking with the parents.

"Officers from Blacktown Police Area Command have commenced an investigation into the circumstances surrounding the child's death," NSW Police said in a statement.

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