I don't think it necessarily tracks that one child will be removed just because another one was, especially 9 years later. That's a really long time, and a lot can have changed. However, if not much has changed in terms of patterns repeating themselves, I would be concerned if I were a social worker. Domestic abuse increases hugely during and immediately after pregnancy, and if you have not got the right support network around you to help, this can be quite hard to overcome when you are feeling vulnerable.
Arguments are stressful, and they must have been significant enough for the police to have been called (although nosy neighbors are a real thing). You might want to go to any meetings prepared to answer questions about it- what were the triggers, why was it so loud, what was the outcome, what process did you use to resolve it, what did you do differently next time to resolve it, what plan do you have in place if it does escalate, and what your partner is doing differently to your ex. They may not ask those questions, but if you go with them prepared in your mind, it will be easier.
I would suggest that you reach out proactively to your safeguarding team, use any help they offer (even if you don't think it is needed) but also be proactive in doing things like reaching out to an organisation you trust. For example, you local children's centre may be able to assign you a case worker who can help advocate for you. I know ours have workers who can access all sorts of services and support, particularly in the early days.
You wouldn't be the first person to be in your situation, and many BPs have been able to go on to parent their children successfully after an adoption (and, for what it is worth, i know myself and most other adoptive parents would be right behind you, fingers crossed and cheering you on to be able to make whatever changes or alterations you need to be able to do it).
I'm sure your head must be all of a muddle right now, so take your time and try not to get too stressed about it. Right now, you and baby need to be able to chill and feel like you are supported, which is what everyone wants. All services involved will know that ultimately, they want the baby to stay with you if at all possible, and will try to help you out a plan together to make that happen.
Please do keep us updated about your progress ♥️