I am not sure precisely what advice you are looking for op?
Advice about how not to feel so bad about rehoming your dog?
By the sound of it, it would be in the best interests of the dog to do so, and also the safest solution for your future children. As long as you rehome them correctly.
The usual route, if your dog came from a reputable breeder where you were able to see the parents in situ, would be to turn to them for help and advice before things got too bad? Why don’t you ask them for advice now?
If you didn’t get this dog from a registered breeder, then I’m afraid I don’t have a lot of sympathy because puppy farms tend to breed for looks over character and do not take the trouble to track the parents blood lines and aggressivity can be unknowingly bred in.
Sorry but you are showing your ignorance of dogs when you say,
“On both occasions there was no warning beforehand.”
Because there is always a warning sign before a dog bites, but it may have been very subtle, or you may not have recognised it as a warning sign, or both. But it would have been there.
For a start, the number of people who still think that a dog lying back offering its belly is automatically a sign that they want to be stroked is crazy! Ask any A&E nurse!
It can be that, but unfortunately it can also be a sign of fear and extreme submission. And if you don’t know the difference between a stiff and relaxed posture then you are asking for trouble if you go in there with your hand.
Again, the signs between the two states are obvious when you know and have studied dog language properly. The dog when submitting like that is saying “stop, I have had enough, big creature x 10 my size, you don’t need to keep leaning in and stroking me and coming after me and touching me. I don’t like it. Look, I am not a threat to you, what more can I do to convince you?” And then if you immediately go in and touch them again, of course it’s going to retaliate to protect itself.
If you are interested in the subject of dog communication then please get hold of a copy of the book ´’On talking terms with dogs; calming signals by Turid Rugaas’ it’s available on Amazon and is one of the best books out there imho.
Does your dog have a safe quiet place where they can retreat to when it is tired and doesn’t want to be touched? Does it have that option?
Also, sorry again, but anyone who sends their dog off to a trainer without being present themselves is showing their ignorance too, unless the dog is doing a high level job like retrieving pheasants or searching for drugs or something. And even then they very often live with their owners during training. The reason why training separately is no good is because it’s usually the owner that needs to be trained just as much as the dog. Plus, your trainer doesn’t sound very competent.
I assume you have been back to the vet to report a change in your dog’s character post surgery? I presume she is not defending herself because she is still in pain somewhere from her operation? How are her hormones? Could they be out of whack? Has all of this been checked?
The other reason why people get in to trouble with daschunds is that they were originally bred for badger hunting and as such need long walks and lots of activities like digging and off lead scent work and people tend to treat them like fluffy lap dogs when they were bred to be independent, active, vocal and brave diggers and hunters.
Is she getting enough exercise and stimulation? Ours can walk for hours. I have never known them to get tired before me and I live on a farm and walk all day!
Your dog sounds fearful to me rather than aggressive per se; bitches can be very sensitive, but you can’t really risk it with a future baby. It’s such a shame that you missed that critical time window in puppy training for exposure to new things, which occurs between three to fourteen weeks. if you don’t familiarise puppies with all of the sights and sounds they are about to encounter in real life then you can end up with a fearful and reactive dog. Why get a puppy and then not put the necessary work in?
Sorry if I sound a bit harsh op, I understand you are very upset at the prospect of her leaving. . But daschunds are not the easiest of dogs to train and shouldn’t be taken on without a huge commitment to understanding their needs. Hence the existence unfortunately of organisations which adopt reactive or aggressive examples of the breed.
I feel upset reading your post because daschunds are usually extremely loyal and devoted to one person and rehoming them can cause them more upset than it might some other more happy go lucky breeds, Although it’s always distressing for both owner and dog, especially when she has been with you since puppyhood.
In this instance though, imho, I think it’s the right thing to do as bluntly you don’t seem to have the skills to handle this. But please make sure she gets passed back to the breeder ideally, or someone they recommend, as the worst possible scenario is that she ends up in another home where she bites again and keeps getting moved from pillar to post, getting more and more aggressive each time. She needs a very knowledgeable home with lots of exercise and opportunity for digging and sniffing about ideally and where she receives lots of time and attention and consistency in her training.