Pitbulls are considered to be high risk dog breeds by home owners insurance companies and they're right about that.
While some Pitbull dogs can be friendly and may not attack someone I've known a few Pitbulls even suddenly snap and turn on and attack and injure or kill it's owner even though they used to be lovely and loving dogs to them.
Never once were they abused or taught to be mean by the owner and still they snapped.
I would never own a Pitbull especially if I had kids around as they're very unpredictable dog breeds and when they attack it's hard to stop the attack unless you're able to shoot and kill the dog during the attack.
So since Pitbull dog breeds are most likely to attack and considered high risk and could injure or kill a neighbor or their kid or even yourself or your family some homeowners insurance will not even accept you or issue you a policy if you have a Pitbull.
If the Homeowners Insurance company does issue you a homeowners insurance policy then yes having the Pitbull will raise your cost of homeowners insurance due to the high risk of the dog and because you'll likely need to put in a claim with the homeowners insurance company should someone be attacked and try to sue you for it.