her body is might just be preparing for labor and birth. she's getting ready
to produce milk.

If she has liquid coming from her nipples then her labor isn't very far off.
Do you have an area set up where she can have the kittens? A quite corner of
a closet is always good - somewhere where she won't be disturbed. Just keep
an eye on her or she's likely to have them on your bed.

I wouldn't expect her to be too vocal once she goes into labor. She's likely
to be breathing heavier than usual and you'll see the stronger contractions.
If you are there when she gives birth just watch to make sure she cleans the
membranes off the kittens faces so they can breathe. Also keep count of the
placentas and make sure she delivers one for each kitten.

http://www.hdw-inc.com/delivery.htm
http://cats.about.com/od/reproduction/a/birthprocess.htm

Just make sure Mom is tending to her kittens and to herself between birthing
kittens. If she isn't and the labor seems to be taking too long contact the
vet.

W