I am pretty sure it is a natural instinct. Your cat will know what to do, but she may have trouble considering it is her first time, (like humans! Walking, talking, you know, everything) Don't worry, she should be fine!!!
Love Always,
Hockey♪

 Don't worry about her giving birth most problems occur if she has the instinct to be a good mom. The body will force the kittens out when its time.

 Nature has a way of instinct kicking in; however sometimes animals have problems giving birth. Keep you veterinarians phone number close by in case she has troubles. Everything should go fine. Try to be with her if you can. Peace.

 It's natural. When you are giving birth you suffer from severe uncomfort and the easiest way to get it out is to...you know.

 It's 100% natural. How do you think first-time human mum's manage it. The cat will know what to do when the time is right.

love PTL x

 A mother in good body condition that has received adequate nutrition during pregnancy is more likely to have a normal labor.  Any mother, human or cat, has a risk for a difficult birth.  Dystocia, difficult/or inability to give birth naturally, can be due to fetal oversize, abnormal birth canal, or uterine weakness.  The first stage of labor typically lasts 6-12 hours--cats may pace, nest, be restless, stop eating, or vomit.  This is the stage when uterine contraction starts and should end with the delivery of the first kitten. 
If this stage lasts longer than 12 hours or you become worried take your cat to a veterinarian immediately.  This can be life threatening.
Hopefully she'll have the kittens at night and you'll wake up to a few surprises!

 They instinctively know how to do this, the only time that they would need help would be in the first delivery, and that would be if she was in labor for a very long time without delivering. If she does this, then you need to get her to the vet as soon as you can, because it could have the potential to kill her. Hope this helps, good luck.