[catlover2]

This sounds like a preliminary stage to birthing to me. You will see when she is in active labour and trying to expel the kitten, sometimes it's a couple of pushes and out it pops, sometime a little longer. If there's active pushing, say, for an hour and no kitten, I would get her to vet as she may have, as 14K suggested, a stillborn kitten, or it might be a difficult breech birth (bottom first instead of head). Another thing to watch for is after delivery of say 2 kittens or more and she has not settled and is still pushing but no kittens, she may develop "uterine inertia" where there are no strong contractions. Get her immediately to a vet as she will need medication to stimulate contractions and may need C-section. Keep calm and give her support if she wants it, and remember complications are the exception, most birthings go well.