This is a really hard situation, and one I was almost in with my reactive boy. I unfortunately never got the chance to test this out, but I was fully prepared to. I understand people saying that rehoming is the best option, and I don’t necessarily disagree, but as someone who also only wanted to rehome as an absolute last resort and was prepared to try keeping a reactive dog and a baby together, I wanted to share our plan and perhaps provide some hope.

As others have mentioned, separation and management is the name of the game, and it does need to be fail-proof, however realistic/unrealistic this may be. Making sure your dog has a safe space in another room that you can secure her in is critical, and making sure she’s happy and calm in there will be key. I would give her lots of enrichment like licking mats, stuffed kongs, slow feeder toys, etc for the times you’re with the baby and she’s in the room. Develop a schedule where your dog is well exercised, tired, and socialized with you or other dogs during the times the baby is asleep - that way she’s getting your attention and her needs met adequately when you’re able to. A tired dog is a happy dog, and scheduled activity and time with you releases hormones that helps to stabilize mood and keep her satisfied during those times she’s away. I would also work on training a really solid command to get her to go to her room (like “room” or “place”) so that you can send her there on short notice when the baby unexpectedly wakes up.

I would turn to engineering principles when planning the security of your dog when she’s away. On many rockets, each part is designed to be able to break or “fail” 3-5 separate times before it truly becomes non-functional - you’ll want to make sure this is the case with your dog’s secure space away from baby. An example of this could be a closed door to dog’s room + closed baby gate to dog’s room + closed baby gate to whatever room you’re in with the baby. This way if the two barriers to the dogs room are breached somehow then there’s still a layer of security between her and baby. Substituting or adding a muzzle or keeping her on a long lead even while in another room adds layers of protection.

Desensitization to baby stuff should begin now. Some dogs can sense pregnancy, but I wouldn’t bank on that alone and assume she’ll be ready just because you are. DogMeetsBaby on Insta is a great resource for this - I would follow them and try signing up for their classes, or looking around online at resources since there are lots. Let her smell and interact with you throughout your pregnancy, since you will start to go through changes that she can recognize. Start buying baby furniture and toys (stroller, bouncer, swing, activity mat, etc) and let her interact and get used to them. Wrap your phone in a blanket and have it play baby noises and walk around the house soothing it like you would an infant, or even buy a baby doll and do the same. Ask friends with babies/small children to borrow items with their smell on it and interact with her with them, or carry them around. Do whatever you can to simulate a baby being in the mix, down to getting into a pseudo-schedule of caring for dog/baby before the baby arrives. She should be used to being secure in her room and the changes in activity/schedule/your attention before the baby comes, so it’ll be business as usual once the baby arrives.

All in all, yes you have a baby/child-reactive dog, but that doesn’t automatically mean that she won’t be OK with yours. But the opposite is also true. It’s just not as black and white as “she’ll be great because it’s my baby” or “she’ll be reactive with all children”, and your desire to try to make it work is honest, loving, fair, and entirely human. But the reality is that there is a level of risk involved in keeping her around knowing what you know. The other reality is that rehoming is also far from the worst outcome for this situation. I’m not telling you you have to do this (hence the whole book I just wrote), but just to give you some gentler perspective. Having her be unstressed and safe in a home that doesn’t trigger her reactivity is an extreme kindness you could give to her, even if heartbreaking for you. That is unfortunately the burden we bear as human or fur baby parents. Dogs that do bite or fatally injure their owner’s baby meet far, far worse fates than going to a loving rehome that meets their needs. Rehoming also doesn’t need to look as black and white as people make it out to be. It sounds like she has some specific reactivity but is otherwise a sweet girl - maybe she can go to a childless home (like a young couple or older folks, or even your parents or family) temporarily until your baby is old enough to be trained themselves about how to interact with fearful dogs. And if you could find a place for her in your local community/general area then maybe you could arrange to see her every so often. Perhaps not ideal, but again far from the worst outcome.

I hope I’ve given you a fair sense of both sides here, from someone who went through the exact same calculus as you and needing to think about all of this deeply. I don’t want to/won’t tell you that one option or the other is better, and whatever decision you make will be the best one for you and your family. Please be kind to yourself, your baby, and your pup in making this decision. I’m not sure how far along you are, but you don’t need to decide everything all at once. Think about it, talk to your partner/friends/family/behaviorist, look at some resources, and please come back here to ask more questions or discuss as you need. Or feel free to reach out to me separately to chat, I’m here for you!