I have not dealt with a pregnant female, but I have introduced a new adult male into my home with an established dominant male bully. I had to introduce them outside of the home first. I read that you did this, how did your female react on the walk? Now when you brought them into the house together, did you let your female into the home first? this is important because your established female will feel threatened if she thinks the new female is trying to take over her territory. Secondly, I would keep them separated by a kiddie gate that they can see each other through so they can get used to the smell and presence of each other. One clue that they are acclimating is the established dog will turn her body sideways to the gate instead of staring head on at the other. this can take up to a good month. Do not rush this process or you will be back to square one. once they are acclimated to your satisfaction, I would slowly introduce them in harnesses and leashed so you can control their contact with each other. You MUST pay careful attention to body language at all times. If see any rigid body language, you must correct this immediately. You can redirect with a stern NO and give the offending dog a tug on the leash. Also watch for any head on staring. This means a fight is coming soon. Same correction can be done. A stern NO STARING, and a tug on the leash. No toys should be available at this time for either dog. This just gives them a reason to try to exert dominance. I also went as far as removing bedding or anything I thought my dominant guy would try to guard. I really went back to basics because I really wanted my guys to get along and believe me, I really did not think it would. I even called the rescue in tears on night telling her my sweet rescue boy Frankie had to go back because I could not take it anymore. Thank god she talked me down and I kept trying and now they are really good buddies. I'm not going to lie to you, it was a month and a half of hell, but in the end it was all worth it. The most important thing is knowing your existing dog and being able to read both dogs body language. If for some reason they get into a real fight, do not try to pull them apart any where near their heads, you will get bit. Instead, grab one of the dogs by their back legs and walk back wards. This puts the dog off balance and makes them release. Good luck. Post any further question you may have.
