kitty in labor

Question
so it's been a week and my cat finally gave birth to two cats yesterday. how long should i wait to gat her spaded
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-----Question-----
so my cat gave birth to a sack yesterday at about 11am but there were no cats. its going on 24hrs. should i be worried? but i can still feel the babies in her stomach and they're moving so they're still alive. so im guessing she will be havint them soon, but when amd what was the empty sack for? or was i some sort of plug thingy? and what do i do when she is in labor? do i help her or just leave her alone?
Thank you, i really appreciate it.
-----Answer-----
This is a question I really don't feel comfortable giving any advice other than take her to a vet just to have her checked out, since you really don't seem too prepared for this event (no offense). When a cat becomes pregnant, kittens are lined up, similar to sausage links, in two separate horns which is the uterus (looks nothing at all like a human uterus). Sometimes a fetus may be reabsorbed by the mother's body, which might be what you saw yesterday.

If she is comfortable, I would make sure she has a nice little box lined with newspaper (don't shred it), and in a quiet area.

But I would still take her to the vet, just to be sure that she doesn't have any kind of fever, or if it's her first litter, for the vet to explain to you the exact things to do when she does have her litter.  

Answer
I would wait until she's done weaning her kittens and to give her body a bit of a 'break'. But, some vets will still spay while the mother cat is nursing, so definitely check with your vet. In the interim she *may* go through a heat cycle, even with nursing kittens, so keep an eye on her (don't let her outside if she's indoors/outdoors) within the next 3-4 weeks - since she could again be bred and pregnant all over again.

And good luck with the two kittens.