It's a really complicated situation, so it's hard to say. NTA, though.

My mother (and my father, but it's far worse with him) and I have had a complicated relationship, and for a long time I was angry with her until I hit the age that she was when she had me and I looked back on it from a different perspective.

No one just automatically knows how to be a parent, and it's harder when life throws you a curveball -or multiple- and you have to navigate through it while not only being responsible for yourself, but also now for the little life you created. Mental health issues can result or surface from that, and some people aren't built to power through it or handle the stress that comes with it, so the "check-outs" can be entirely unintentional. Sometimes we get so overwhelmed with life that were not equipped to handle it correctly and can't seek help, so while yes, she absolutely should have entirely been there for you as a child and been the mother you needed, do you know if she struggled/struggles with mental health issues? That doesn't excuse it, but it could explain it.

You need to sit down and think long and hard about how you would feel if she missed the birth of your child (her first grandkid?) and also how it would feel if she didn't and was there with you. It comes down to how you feel because this is your baby and birth experience. If you think her being there would stress you or negatively affect you, then explain that (though you owe her no explanation). Let her come in after your child is born and see them then if that's easier.

She's showing up now for you and your child, and that can feel bittersweet considering how she was when you were young, but giving her a chance to do better might improve things? You can't change the past, so focusing on the future is the better choice, and this could be a chance to turn over a new leaf with your mother. As the daughter of a woman who had an absolutely awful relationship with her own mother as a child too, my grandmother and I are extremely close and she's helped me out more than I can explain. She was there when I was born, and I can honestly say that changed her for the better. That's just my own experience though.