Towards the end of my wifes term her ankles swole up very much so...our doc said that their body starts to up the volume of blood and water when it knows that birth is close. Sure enough she went into labor the next week.
All you can do bro is make her comfy...draw her a bath, put her feet up, bust out the lotion and rub her down. Keep her off her feet if you can with simple shit like you doing dishes, vacuuming...things that require long standing periods. It sucks but honestly to this day she still talks about how I stepped up when she needed me. Plus it's nice to have something to throw in her face when she spouts the "you don't ever take care of me.." when in her PMS rage.

Hang tough bro...when your child is staring you in the face, you'll know it was worth it.