OP, I totally get where you're coming from. My parents are still together, but my father is a violent, damaged man who made my childhood a misery and my mother, who I always considered a victim, I've now realised is just as much the problem as he is, as she facilitates his behaviour and endlessly covers up and compensates to save face, no matter what it costs her or her children. I feel sorry for her, but it's psychotic how she's so happy to sacrifice her children and friends and family to protect this man and keep up a facade no one believes. She cannot admit to the world how bad it is and that a nice middle class well educated woman like her could be taken in by such a lying nasty shit for 40 years.
Anyway, I moved to the other side of the world when I was 19 to get free of all the shit, but I still kept in contact with my mother. What I didn't realise until about five years ago, when it dawned on me that she almost as bad as he is, is that, in my absence, my mother had been rewriting my childhood and repackaging it as perfect and my father as a saint. She even came up with this tall story that I'd left the country because my cousins bullied me, which i only found out about when one of them, deeply hurt, asked me if this was true - I was utterly bewildered until I realised what was going on. When I twigged to what extent this had been going on and objected, my mother went mental and put enormous pressure on me to toe the party line and go along with her fantasy. Basic facts of my life had been twisted out of all recognition. Utterly disturbing. And she was desperate for me to play along. Not happening. She chose to be with him, I didn't. Why do i need to facilitate him too? Anyway, after a year of manipulative hell, I decided, with the full support of my partner, that it was healthier to cut contact altogether (he rang up and told her, to keep things as clean as possible), but, every now and then there is a new attempt to drag me back into the shit storm. For example, I had a huge wobble when there was a new attack timed for my wedding day, which involved other family members who she'd roped in and who were deeply uncomfortable about it but didn't feel they could say no. No one wants anything tainting their wedding day and we had made it crystal clear that they weren't invited and we wanted no contact, but she couldn't respect our wishes and had to mess with me.
So, soon after I discovered i was pregnant, like you, I started to freak out about what might be in store re my parents. For a long time I hadn't wanted children, as part of me was worried I'd repeat the same patterns, so it's a big deal my getting pregnant and I feel very vulnerable. I knew they would find out sooner or later, as there is family I'm in contact with who are still in contact with them (unlike my mother, i never badmouthed her to others and never asked that anyone take sides, always saying the minimum and insisting it was between us - I couldn't do that to her, even though it's been heartbreaking that some family members I loved have turned against me because they believe the horrible things she says about her own child, but then they're over there and I'm here and it's 'out of sight, out of mind' and they knew me at 19, not now), but it was horrible not having any control over when and how and feeling like I was always waiting for the other shoe to drop. Wondering when they'd kick off, just when i'm feeling so vulnerable. I also didn;t want the family I am in contact with put in an awkward position or dragged into anything a la the wedding. We hummed and haaed, but we've now decided that, once i've had my 12-week scan, my husband is going to email my mother and state that we're having a baby but that nothing has changed and that we want no contact whatsoever. That way, we control when and how and aunts and uncles and cousins don't have to worry about putting their foot in it or telling them anything we don't want them to know. I'm still a bit twitchy about photographs etc. Most people would respect my feelings, I know, but my godfather, who's an old fool and utterly insensitive, sent them photos of my wedding, which upset me, but then he had a relationship with them before i was even born, so I wouldn't ever ask him to choose (too afraid that he'll ditch me as certain other family members have, as my mother throws mud and i don;t and they swallow what she says about me, as I'm not about to defend myself).
Long, rambling message, but it's not just you, believe me. Like me, i bet you're envious of all those who have loving, supportive families, but that's just how it is. And we can do better with this new generation. I'm determined that none of this shit will get anywhere near my child. When they're an adult, they can make their own decisions about whether to have any contact with their grandparents, but, until then, if my father or mother want access to my child, it's over my dead body.