Please Help! Cat in Labor! How Long inbetween Kittens

My cat surprised me in labor this afternoon. She gave birth very quickly to 2 kittens and I felt a 3rd one kick but it's been almost 3 hours and no activity. How long can she go inbetween kittens before I need to worry? Thanks.

my kitty serena had one kitten on Monday and two kittens on Thursday but  if she shows any signs of distress take her in to the vet asap fever heavy panting straining to push seeming lethargic etc....

She went three days between kittens? That's Normal? Omg wow she is doing good eating and nursing her two she has now but I definitely feel one more in there

yes the vet said its not very common but it dose happen her first baby dident survive he may have ben premature and she seemed to lack milk  the other two were born on the 18th there happy and healthy gaining weight every day and have there eyes open today hope your kitty delivers her last little one safe and sound 

any more kittens?