Betsy said it well. But many don't know this cause it's still considered "best" to have a person "push til 10", holding her breath the whole time, (purple pushing I call it), and stretching the perineum ("ironing" it's often called) are used all the time. Both practices are being questioned these days for the reasons already stated. Pushing to 10 tires a mom out and reduces oxygen available to the baby. It's very, very strenuous and a person can only do this so long before becoming exhausted. And her baby needs all the oxygen he/she can get in labor as the stress of labor will reduce oxygen available to him/her just in the contractions it produces.
If a person chooses to be coached to push, and wants someone to count, I usually only have them push to 6 or 7, not 10. Also, stretching the perineum can be harmful and create inflammation, making it subject to tearing. It's far better to let the baby come down slowly, letting nature stretch the perineum gradually. Applying heated compresses to the perineum is often helpful and can feel VERY good to the mother. Some midwives like to use warmed olive oil for this purpose, or warm, wet washcloths, like we use at the hospital.
Betsy is right--- the longer we keep the doctor out of the room, the less manipulation to "hurry things along" there likely will be. I wait with primips to get the doctor over until the baby is nearly crowning usually (the doctors are at home at night). And with multips, have the doctor aware they might want to come in, when they are about 8cm if they are moving fast. Then, I tell them when they get to the hospital, I will call them in when they are needed and equipment is ready. Usually, they are happy to rest in the lounge or watch TV until that time (it is night shift and that is a distinct advantage we have at night). The doctors do not want to sit thru extended pushing either, where I work.
And yes, "laboring down" is invaluable. Especially in the presence of epidural anesthesia, the uterus can push that baby down all by itself with no effort from mom, conserving her energy and oxygen for baby. I always let a mom labor down unless a baby is in trouble, at which point, the doctor will be called in to assess the situation. Leave her alone! Let her rest til the baby is nearly ready to crown and she will THANK YOU! Believe me.
A mom without anesthesia will "feel" what is right to do, if we let her. She can tell us what she needs to do, more often than not. She will "grunt" and "groan" her contractions, (in the transition and final phases) gently pushing the baby down with these efforts. Almost NO mom will naturally push, holding her breath to a count of ten, to get her baby out. She will more likely push in spurts, to relieve the tremendous pressure she feels during each contraction. This is a good thing! Seems nature has a way of taking over and they just do what comes to them, and all I do is keep them focused and reassure them what they are feeling is normal and ok. I listen to them, keeping my mouth SHUT unless they NEED me to intervene. The baby will come down faster and better if they are sitting, squatting, standing, anything but laying on their backs. I have them sit on the toilet or chair more often than not to help them with this and sometimes, babies literally FLY down as they squat. This is truly amazing to behold.
Hope all this helps you. The more we let nature take its course, the less likely tearing and instrumental intervention will be needed, most of the time.