Mattress protection

I'm 39 weeks today and washing our sheets. Before I put the clean set on im tempted to put a chux pad down. Normally chux pads are small, disposable, and make noise when you move but i got a huge fabric one with a waterproof lining sewn on from my grandparents.

Is this a good idea? I got the chux pads for after baby comes jic I bleed through during the night but now I'm thinking what if my water breaks during the night? I know it should be clear anyway but my husband really loves our mattress and its pretty new soni thought he'd appreciate me saving it from any fluids.

Can your water even break during the night or does that normally happen when you're up and about? I'm a FTM so any suggestions are welcome.

**Update!

Follow up question, should I put the chux pad under or on top of the sheets?