PIPed while 9 months pregnant

I worked at my current company for 2 years. I got a promotion in first 6 months. I have been a high performing employee. i took over all the work, trained everyone and kept the ship afloat when my manager went on her maternity leave.
I got pregnant after and let my company know. I also hired and trained a team to get the work done. My manager started lashing out on me on unreasonable things after she came back. I thought she was trying to establish her control again or was going through something so I let it go. She has been trying to find my faults in random things even petty small things. I was very polite but she wouldn't leave any opportunity to highlight the minor issues in emails to entire group and higher ups.
I went on vacation and before I left there was a problem in one of my projects. I was swamped with work and put in so much extra effort to fix the problem which I did. After I came back, she completely changed. She started assigning my projects to other people, took over my team without asking me. she still kept on belittling me, making sarcastic comments. She started hiding things from me. She escalated her attacks on me and in my review, gave me a performance improvement plan. Before that she lashed out at me in front of my colleagues and my direct reports, blamed me for things as if trying to set me up. HR was there in my review and she gave me a PIP which was fabricated.
She didn't care that I was 9 months pregnant, so close to my labor. All she cared was how I'm going to transition my projects and kept on reminding me of that. I tried to explain my position to the HR but it was of no use. i couldn't resist but writing a rebuttal to that PIP explaining my story with facts and evidence.
My health was deteriorating. After I wrote my response, They discussed all the points and the higher ups acknowledged that' it's a miscommunication problem but the manager didn't back down. Eventually the HR sided with her and they retracted few points but didn't take the entire PIP back. No one seemed to notice my pregnancy and that I was in so much stress etc etc, all they cared was me to improve in my 9th month on things that were made up. the higher ups agreed with me on everything but said that they cant do anything to help. My doctor was worried about my health and took me out due to health reasons which led me to start my maternity a month early.

They stopped my PIP but wanted to start the clock once I came back after the leave. they even wanted me to blame my direct report but I didn't do that. My doctor removed me from that situation but it put me through a lot of stress.
Upon return, they gave me the same PIP on the first day so I gave notice the same day.

I wonder if this is a norm in most companies?