So I'm wondering, how often do you call or see your mum? Do you live close? Go on holiday together?
I have a very poor relationship with my mum. She lives about 3 hours away from here. I wouldn't want to go on holiday with her. I did once (foolishly) accept an offer for her to take me, my ex and the DC on a holiday to Disneyland Paris. It was very generous, but (as always) came with the expectation that she could control everything we did and ended up being very stressful. I ended up properly ill and my ex had to put his foot down over some food-related decisions which she decided was evidence of him being evil. So never again. Ever.
I haven't seen her since Boxing day, or spoken to her. I've exchanged a handful of messages with her in that time. She messaged me at the weekend asking if she could come next weekend. I didn't respond until she'd sent me another message this morning basically demanding I respond to her request. So I lied and said I was ill and just put her off. I have some specific reasons why next week is not good anyway (I'm due to have a baby on Friday - but I haven't actually told her about the pregnancy yet for a range of reasons; I'm pretty sure DS1 has told her, which is why she's asking specifically about this weekend in a passive aggressive manner).
Thing is, I just don't trust her. She's very overbearing and controlling (albeit often in weird ways that look from the outside like generosity). As I've gotten older and further away from her I've had time and space to recognise this properly and reflect upon all the ways that it can never be a great relationship. As a teenager I endured what I can know recognise as emotional abuse from both my (divorcing) parents who were determined to alienate me from each other, and generally just fuck me up. My dad was actually just the less effective manipulator, so I went NC with him years ago (so my mum decided she'd 'won'). But actually, my mum was just as bad; she's just smarter about it all, and plays the victim better.
Similarly, she's always been the sort of person who makes a huge show of how wonderful and helpful she is. But actually, it's all just about control. If you're doing what she wants, she'll be so generous and nice (but will tell the whole world all about how wonderful she is etc). The minute you make a decision that she doesn't want you to make, and she's no help at all or outright obstructive. For example, I had to give up a place at Cambridge university and go to my local university because she absolutely would not help me (financially, practically, otherwise) to take it up because she wanted me to stay at home. She was delighted to tell everyone about her smart daughter who 'turned Cambridge down' though.
The current dire state of the relationship definitely isn't helped by the fact that she's purposefully cultivated a really weird relationship with my eldest son (now 20) where she basically has claimed him as her son rather than grandson. It's weird, creepy and unhelpful (to me and him, but I literally can do nothing about it now). It also doesn't help that she's regularly a total dick to DH either (but in sly and passive aggressive ways). I think this is largely because she realises she can't control him, and he's a significant barrier to her controlling me.
Despite this, DH is utterly bemused that I haven't told her about the pregnancy. But we've been in lockdown (so it hasn't been a necessity) and, more importantly, I just don't trust her not to be a complete arsehole and ruin yet another pregnancy. She behaved appallingly when my DS2 was born and caused enormous amounts of stress and upset. After the birth she briefly saw him for about 10 minutes and then I didn't see her again for about a year. I just refuse to give her any opportunity to do anything of the sort this time around (and, let's face it, the whole virus thing has made being pregnant pretty crap anyway right now). I have now realised that I won't ever be able to forgive her for what happened last time. I'll tell her once the baby is born, but who knows how she'll react about the just not saying anything.
My sister is very close to my mum, and I've never been close to her (we're very different people). I haven't told her about the pregnancy because she's already made it very clear (when I first met DH) that she thinks we should have no more children. She was enormously judgemental about it - but I don't care about her opinions. She's judgemental about just about everything (but is on thin ice in most of her judgements anyway).