To not want my parents to go in my bedroom (I'm 33 yrs old)

With your updates
and the enforced open door bathroom policy throughout your teens and twenties

I am speechless you are leaving your baby in their sole care

I mean, this.

Is their bedroom off limits to you?

I wouldn't think twice about entering my parents bedroom so it goes both ways.

The point is that it's a favour, not a professional service and that it's provided within the usual reciprocity of a family. You can sit down and 'redraw the boundaries' and potentially lose all the goodwill in the arrangement. It seems a big price to pay for putting away any personal items and making your bed.

Given your past experience and your sensitivities it would be better for your relationship with your mum, if childcare wasn't at yours so that she isn't left alone at your house.

You know how she behaves and don't trust her. If you are still struggling then the arrangement isn't right. Change it.

You know the saying ‘the definition of insanity is doing the same thing over and over and expecting different results.’.(Albert Einstein)

Yikes!!

hold up… you are the poster who’s parents had an open door policy to the bathroom even in to your teens and 20s!! Mum and dad would both come in while we were in the bath to ask something, or wash hands in bath water (went on into our 20s. We'd also have to take things in to them when they were in the bath

so this entering your bedroom is surely no surprise to you whatsoever! (And very civilised of them considering bathroom open door policy!)

But there is no reason she needs to go in so nothing in there has connections to looking after a child

I'm surprised so many people think you are over reacting. Babysitting doesn't give the right to overstep. From what you've said, I think your mum finds snooping acceptable. I would prob just get a lock for the door or just leave out the biggest dildo ever on your bed, that'll make her regret being nosey surely 😂

Your update puts a slightly different slant on it.

Initially I thought you were being unfair, but after your update, then I don't think you are. In fact, knowing what she was like in the past, I wouldn't be overly keen on this childcare arrangement - I would prefer it to happen in her house. Difficult if it's free, though.

So, with your update in mind, no you are not unreasonable and I would be looking to revise the childcare arrangements to avoid her being in the house and having opportunity to repeat the same behaviours.

I’m with you OP, it’s snooping and I wouldn’t like it either.

They have no reason to be in your bedroom if the door is firmly shut, and that will stop the baby crawling in there (which sounds like a shite story anyway)
Get a lock if needed.

I do think you are entitled to privacy even if you are getting "free childcare"

In that case you're going to have to speak to her.
Does she have form for pushing boundaries?
I don't understand pp saying you have to put up with it bc you're getting free childcare.

Where are you meant to draw the line, oh DM is rearranging my cupboards, digging up my garden, painted the front door purple but it's ok bc she gives me free childcare.

Keep the door closed
that will mean baby can’t crawl in there
thank mum profusely for doing laundry and say you like it to be left in the spare bedroom or if you don’t have one, the nursery

You knew she was nosy before you asked her to babysit, nosy parents don't change, keep stuff you don't want her to see hidden/locked away and leave her to it , you could maybe have her watch the baby at her house if you think it's too much temptation at yours

Yeah. But then they should pay for childcare.

I wouldn't like that either. I also think a bedroom is a private space. I don't turn up at my parents house and start wandering into their bedroom. Can she have your son at her house instead of yours? I'd be too distracted to work with both at my house.

The rare trip inside your bedroom is a small price to pay for free childcare, who come to your house, allowing you to work (with bonus ironing thrown in) … and I’m guessing it’s not just the ironing they look after.

Ungrateful isn’t the word … if you are that bothered get paid for childcare.

You might not have a problem with your mum, but OP - and her DP - are entitlef to have their own boundaries, no?

My stepmother in law has done this, including putting clothes away, and I hate it.

Can you say something to your parents like this
"Mum and Dad, we are so grateful for everything you do, but we would ask please that you don't come into our bedroom while you are here. I sometimes leave washing or dirty clothes lying about and I don't want you to see my mess in my and DP's private space. It feels very intrusive, and that might seem silly but it is DP's space too. It was very kind of you to do the ironing, but I would rather you focused on my DC. If she's crawling, it's better there aren't hot irons around."

Agree. If you both have an issue with it, pay for childcare.

This wouldn’t bother me at all. And your mum has done you a favour by trying to help. If you don’t want her to, just pay for childcare. Or just tell her not to go in your room…

I dont think its unreasonable at all to expect them not to go in there unless they specifically need to.
I think bedrooms are your private space, I never go wondering around anybody's home. I would only go into a room if I was invited in or asked to go in.
I'd close your bedroom door and see how it goes. If they go into your room again then I'd just politely say mum could you not go into my room please, I may have personal things laying about.