I'm honestly sorry to hear this - you don't need this right now in your stage of pregnancy. Your going to be having a lot on your plate in the next few months- please don't "yell" @ me for saying this but have you thought of rehoming one of them? Or separating them?
This is what happens (so I've heard) when you have 3 females in a household. Which one is dominant? And does the other one want to be 'queen'?
I know you don't believe in disposable pets and neither do I. I'm absolutely against it. BUT your first priority in the next few months is your new son. And if something would happen to him if the dogs get into it - you would never forgive yourself or the dogs. I'm not implying that the dogs or the baby are 'more important' but BOTH are 'helpless' and both of them need YOU to do what's right for them.
I wish you LUCK from the bottom of my heart.