dog misbehaving and I am pregnant

Question
So my do has been a very good guy, never urinated in the house after we houesbroke him.  I am 37 weeks pregnant and he was on his bed(which has not been washed) and was doing his usual thing (digging to get the comfortable spot) and out of nowhere he started urinating on his bed.  It caught me off guard!  I have heard that dogs will misbehave when a person is pregnant and they know there territory is going to be invaded, but I did not believe it.  Any thoughts would help!  Thanks

Answer
There is no doubt dogs can sense pregnancy and it brings changes of behavior.  Exactly what is happening is hard to say and it varies.  

The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat.