There is something about the energy in a pregnant woman's body. Many people call it a "glow." It is an intense and incredible responsibility to provide shelter for another life and then to bring it into the world. Everywhere the laboring mother puts her feet becomes sacred ground, from the bathroom to the hallway.
It doesn't take much to disrupt this energy flow. You hear countless stories of women in active labor who get to the hospital and suddenly everything stops, or contractions slow down significantly. It's a powerful force and one that is best left to progress on it's own.
This is why it is so important to give great consideration to who is allowed to visit and attend you while you are in labor. Everyone who comes in contact with you needs to be on the same page as you are. If your desire is an unmedicated birth, a well meaning friend stopping by and saying, "I don't know why you are choosing to be miserable!" is not encouraging your process. The woman in labor is vulnerable and her words may very well ring in your brain later when you are facing your most difficult contractions. You may temporarily doubt your own choices.
In her book, Spiritual Midwifery, Ina May Gaskin has this to say about it: "The birthing energy flows smoothest when everyone present is part of the crew, helping the baby to its birth. If some of the other people present are spectators, or what we call "passengers," the birth can be slowed down by hours or can even be halted until some change takes place in the energy. This is because anyone whose presence is not an actual help is requiring the emotional support that should be going to the mother."
Talk to your labor attendant about how to handle keeping your birth space sacred in the home and in the hospital. Incorporate some boundaries into your birth plan. Talk to your care provider about laboring at home as long as possible to avoid unnecessary people coming in and out of your space while you labor. It may feel selfish to you to allow only your husband to be in the room. But remember that you are ultimately creating an environment for your baby's birth, not just for yourself.
I recommend reading Ina Mays Guide to Childbirth if you want to find out more about birth energy. It contains wonderful birth stories and great information for the empowered woman.