Many times in my class pregnant mamas ask this question "How will I know I am in labor?" or "How do I know when to call the midwife or go to birth center/hospital".   When I was pregnant I remember thinking the same thing.  Its like having a really bad map and venturing out on a boat looking for something that no one has explained very well and that you have never seen before.  First of all with this example you can see the importance here of having a tour guide, a doula :).  But more importantly here is the fact that this experience, giving birth, is not something that happens to you or outside of you.  The birth experience is a part of you and very internal.  You cannot plan it like a trip.  But you can practice awareness of mind and body through meditation, breathing and staying calm.   Since I have starting teaching prenatal yoga and then attending some of my student's births I have noticed a huge shift in their experience.  Even though the temptation to panic is there, just like if you were in the middle of the ocean and did not know where land was, these yogis don't.  What do they do, you may wonder.  They breathe, they stay with it as if it were a beautiful asana(yoga pose).  The most important thing to remember here is that if you focus your attention throughout your pregnancy to calming the mind, breathing deeply and listening to your body you will know when the time has come to birth.  Granted many of us in labor don't wait until that inner knowing moment and we just want it to be done!  But if we surrender and ride the waves, our body will do the work and tell us when to really get to where we need to be.