Purple pushing, also described as Valsalva pushing, is when you get to 10 cm and the doctor and the nurses order you to "PUSH" but you are not feeling it. You are forcing yourself to push, but your body is not ready.
Many times they ask the mom to push, when is not ready, laying down, and in stirrups, where it may cause tears, and endanger the baby, because gravity many times is not helping, and a decrease of oxygen in the body to mom and baby can occur.
In Birthing Naturally, a post is dedicated to pushing, Birth Plan Options: Pushing, the break down "pushing" to three types, "Directed or Purple Pushing", "Spontaneous or Mother Directed Pushing" and "Exhale Pushing." There are benefits to directed pushing and the only one I see is for those that are managing labor, and want to get out quickly, the author states, "This style of pushing can be helpful it there is concern for your baby's health because directed pushing does decrease the amount of time spent in second stage labor." Now the side effects are, "directed pushing does increase the chance of a tear, increases the mother's fatigue and can decrease oxygen levels for both mother and baby." Spontaneous pushing decreases the chance of tearing, and Exhale pushing, helps the mother relax if they can coordinate the breathing with the pushing.
This blog that I found has a nice description about purple pushing. She describes a situation where you have eaten dinner, and than you are told go to the bathroom to poop...The logic is the same, you don't direct someone to poop, you just let them go when their heart desires...Purple Pushing: Just Say No
In this article, posted by Karen, called Pushing: Woman to Woman Childbirth Education again she goes ahead and talks about how impractical it is to tell a woman to push, when she is fully dilated. She explains that there is a latent period, and that there may be a period where "nature" is giving the woman a "break" before she has to push the baby out after enduring the contractions. I prefer this last blog as it offered a study of 39 first time moms that were allowed to do spontaneous pushing and had "intact perineums postpartum"
Again the same line is repeated, manage pushing helps decrease time in labor, but offer three serious side effect that anyone would like to avoid. Spontaneous pushing during birth: Relationship to perineal outcomes reached the following conclusion: “These studies indicate that the only apparent advantage of Valsalva pushing is a shorter second stage, which, on occasion, may be desirable. However, expediting delivery by forceful, directed pushing is achieved at the expense of three negative outcomes: reduced oxygenation of the fetus, more frequent trauma to the birth canal, and potential injury to future pelvic floor function.” The above study was published on February 12, 1999.
Another issue, discussed in the last article, is having an epidural. When you have an epidural, you lose sensation, and therefore you cannot feel when you have the urge to push. In this instance, you need to be directed, but again the dangers to the pelvic floor and perineum continue to be the same. An epidural is again managed labor, which with all the risks involved, most women should avoid and learn to trust and know their bodies.