I have a waterproof mattress pad on my bed - bare mattress then regular mattress pad, bottom and top sheet covered by waterproof mattress pad, top and bottom sheet. I didn't birth on it last time but have the twin sized version on my son's bed and he's never peed through it! It's just the Target brand pad.
I've heard of women using some other waterproof something to drape over the side of the bed. I suppose that's to protect the box springs or a bed skirt or....something I'm not worried about. I can't imagine using anything plasticy like a shower curtain or plastic sheeting. We have all hardwood but I did remove the rugs that were in our bedroom. I've read of a roll of sticky plastic sheeting that can be laid on carpet. I think I saw that in the HB forum under a stickied (at some point) thread.
I personally wouldn't throw away a waterproof mattress pad just because it got birth fluid on it - I'd wash it and if it were stained I'd be putting a sheet on it anyhow. Maybe I'm gross? I would discard a cheap sheet though. I think the ones I have packed for birth are light coloured like yellow and pale blue and green. I didn't but new sets, just didn't put the pricey ones on. I don't plan on birthing on the bed and would have Chux and such for lochia.
Under my pool will be a tarp (like used in camping) covered by a blanket because I don't want to step out on plastic. If I'm bleeding I'll have a towel put on top of the blanket first.
My MW has me put together a bundle for mama, baby and compresses. They're sealed in garbage bags, taped, in a bin bedside and contain -
2 fitted sheets, pillowcases (?), 2 pair of underwear and 2 bath towels for me
2 regular but soft towels (these are $5 towels from Target), 8 receiving blankets, baby clothes - t's, one pieces, onesies, socks, hats, cloth diapers for baby
24 small washcloths, a dishtowel and 2 hand towels in the compress bag.

There's a Crock Pot on my dresser along with some cleared off space for the MW's things. I have a lightweight, black cotton robe on a hook inside my closet which will be right beside the pool if I want to throw it on upon stepping out. I'll need to set out a small bit of PP clothing on a dresser - a gown, some yoga pants and tank, nursing bra.
I also have two towels with my pool stuff. I'll want this for draping over the side so I don't have to lean my labouring face on plastic and for drying off. I see my theme - don't touch plastic while labouring. Anyhow, there are also other towels nearby in case I need them. With my last birth I used 3 tops. I'm probably over prepared when it comes to towels. Pool stuff = bucket, hose, blanket, tarp, towels, fish net, extra adapters (the one I'm using is currently on the sink), digital aquarium thermometer, pool instructions and patches. I don't have my pool blown up because the second I ordered arrived this afternoon (the current version of the fishy pool is trashy IMO so I bought a La Bassine) but I will have it inflated and tested very soon. I have a plugged in electric pump in my SO's bedside drawer. He'll empty via siphoning.

I have a basket of birth stuff - glass bowl for the placenta (I need to get another in here for potential vomit), Chux, an enema (what is this for in regard to the labouring woman?), a roll of soft paper towels, bendy straws, gauze pads, 2 lady pads for immediatley postpartum, a bulb syringe...

...and a little bag containing a list (on a Pride & Prejudice & Zombies postcard) of what's inside - Clindamycin, trash bags, peri bottle, arnica and olive oil, thermometer, antibacterial soap and a waterproof flashlight.

Bedside I have a basket with diapers and wipes and a Boppy

On my nightstand is a basket with some postpartum stuff like Advil, Tylenol, arnica, Lansinoh, pony tail holders, lip stuff, ThermaCare heating things. I also have a heating pad plugged in and tucked between the table and bed. I need to put a baby outfit or two and some Aiden & Anais blankets nearby as well.

In the bathroom I have a basket containing pads (smaller sizes are in a closet), stretchy nylon Hanes boy short underpants, Tucks, a peri bottle, EMAB bottom balm and spray.

On my SO's bedside table and under the phone is a handout with hospital directions and a postcard containing directions from our home as well as emergency contact info and our info. I suppose I need to pack a hospital bag and write a list of what to take on the fly should the need arise.

I don't think a lot of this will be used and I'll be left with a bedroom of chaos and tons of linens to put away, things to return to the store, etc.
I've also put great thought into lighting so that's taken care of by a soft lamp, a string of pink Xmas lights and flameless candles. Because this stuff is important when it comes to birth 
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