Darla Napora, 32, was mauled to death by her unneutered Pit Bull, and was found dead on the sitting room floor of her California home by her husband Greg.
Police shot the two-year-old dog dead when they arrived at the scene.
Darla Napora was a member of Bay Area Dog Lovers Responsible About Pit Bulls group, who campaign to change attitudes towards the breed and convince people they aren't dangerous.
Pacifica Police Captain Dave Bretini told reporters: 'When they arrived, they found the victim laying in her own front living room; she was not breathing, unresponsive and had major trauma to her upper body. The husband stated that when he got home, at about noon, he found his wife with their pit bull hovering over her.'
He went on to explain that they shot the dog in case it attacked passers-by:
'The last thing we wanted to happen was for the dog to get out and start attacking bystanders or be loose in the neighbourhood. So as soon as the dog got out of the backyard, the decision was immediately made to put that dog down and that's why the dog was shot three times by two officers on scene.'
Darla's husband insists their dead pet will be buried with his wife - and maintains the dogs are NOT dangerous.
One of the family's neighbours said the dogs had always been well behaved, whilst another told journalists he thought the breed were dangerous and would not allow them near his family.
It has not been reported how far along Mrs Napora was in her pregnancy.