The Law of the 3 P's vs. Sphincter Law

This weekend, I had the privilege of attending a workshop on Pain vs. Suffering presented by Penny Simkin, noted author, doula and one of the founders of DONA (Doulas of North America). During her talk, I kept thinking back to Ina May Gaskin’s discussion of the physical workings of labor, and how emotions and how a woman feels plays even more important a role in how her labor progresses than the strength of contractions, position of baby, and size of a mother’s pelvis. Ms. Simkin brought up how a woman’s past can have a huge affect on her labor. Abuse, trauma, and shame can lead to fear and suffering during an event that should be celebrated. This makes perfect sense, and physicians normally take past history into account when working with a patient. But when it comes to a woman who does not have a past history, physicians rely heavily on the Law of the Three P’s for understanding progress and time of labor.

I first read about the Law of the Three P’s along with Sphincter Law a few years back in the book, Ina May’s Guide to Childbirth. It sparked an interest in me, but not until this year have I really dug deeper into understanding the differences between the two and how they really play out in childbirth.

What is the Law of the Three P’s?
The basics of the law say that:
• A woman’s body, if it is capable of giving birth, should produce a baby in a reasonable amount of time.
• If progress is not apparent, one of the three P’s is dysfunctional, and intervention becomes necessary.
• Strength of uterine contractions (Powers), size and position of baby (Passenger), and/or type and dimension of pelvis (Passage) are the main components in a labor’s progress or dysfunction.


First, let’s look into what a “reasonable amount of time” really amounts to. In the 1950’s an OB resident at Columbia-Presbyterian’s Sloane Hospital for Women in New York took on a project of plotting the progress of labor in each of the laboring women in his ward. With the initial intent of seeing if caudal anesthesia had any impact of the speed of labor, Emanuel Friedman unknowingly changed the course of obstetrics by presenting for the first time an average length of time of the three stages of labor. While he considered the information to be used to help doctors determine if their patient’s progress was well outside of normal, Friedman became frustrated when he saw that doctors used the averages as absolutes, not taking into consideration how many women fall on either side of his asymmetrical bell curve.



In Norwitz and Schorge’s book, Obstetrics and Gynecology at a Glance, a “dysfunctional labor” is diagnosed if, during the active phase of labor, a first time mom is dilating less than 1.2 centimeters per hour and/or baby is descending less than 1 centimeter an hour. In a mom who is having a second (third, fourth, etc.) baby, dysfunction is diagnosed if she is dilating less than 1.5 centimeters an hour, and/or baby is descending less than 2 centimeters an hour. An “arrested” labor is diagnosed if a mother has not progressed in dilation for more than two hours, or progressed in baby’s descent for more than one hour in multiparas and two hours for first time moms.

How limiting! Within only these very narrow margins, a “normal” labor is considered. If a woman falls outside these margins, then the first step is to augment the Powers, the first thought being that the uterus is dysfunctional in being able to produce strong enough contractions to get the baby out. If mom doesn’t get on track with augmentation, then baby or pelvis must be to blame, and cesarean is considered the only way for baby to get out.

Since uterine contractions, baby and pelvis seem to be the main parts of laboring, this law may seem reasonable. But it definitely puts limits on a woman’s abilities and does not take into account that the uterus does not work apart from a woman’s brain.





Understanding the Laboring Brain

From the works of Michel Odent, we are able to see how much the brain is involved in labor. The brain is made of two layers – the primitive brain, and the neocortex. The Neocortex is the newer, rational part of the brain, which plays a role in abstract thought. The Primitive part of the brain, also called the brain stem, governs instinct and is considered to be a gland that releases hormones.

Labor is all about hormones! Oxytocin, endorphins, prolactin, etc. are all released by the primitive part of the brain. Dr. Odent likes to call it a “labor hormone cocktail”. No amount of thought or rationalizing will be able to make more hormones to produce the proper workings of labor. In order for these hormones to be produced, a laboring woman must allow her primitive brain to take over. In natural births, you see this in women who are laboring. You can tell when a woman has gone deep into “laborland”, and is no longer aware of what’s going on around her.

But what happens when we force that woman out of her primitive brain? Stimulating the neocortex by asking a laboring woman to answer questions that require thought, being near her in a way that makes her feel self-conscious, subjecting her to bright light, or failing to protect her privacy can actually inhibit the action of the primitive brain in hormone release. So, in reality, much of what goes on in a hospital room is working against the entire labor process.

How Sphincter Law differs from the Law of the Three P’s
While the Law of the Three P’s takes only three physical parts of the body into account for labor progress, Sphincter Law takes a look at the woman as a whole being, and considers that the cervix and vagina, being sphincter muscles, are highly responsive to fluctuation of maternal emotions.



The basics of Sphincter Law say that:
• excretory, cervical, and vaginal sphincters function best in an atmosphere of intimacy and privacy.
• these sphincters cannot be opened at will and do not respond well to commands
• when a person’s sphincter is in the process of opening, it may suddenly close down if that person becomes upset, frightened, humiliated, or self-concious
• the state of relaxation of the mouth and jaw is directly correlated to the ability of the cervix, the vagina, and the anus to open to full capacity.

Consider what your needs are when having a bowel movement. In order for that sphincter muscle to relax and open fully, most desire a moment of privacy. If, in the midst of a bowel movement, the bathroom door was suddenly thrown open, what would happen? The sphincter muscle would probably tighten back up. It is also necessary to be comfortable and relaxed in order to have a bowel movement. I know people who have a hard time with bowel movements if they can’t take off their shoes. If you are stressed and rushed, bowel movements may not occur. When you consider that the cervix is a sphincter muscle as well, it makes perfect sense that the needs for bowel movements would be similar to the needs of having a baby.

If the Law of the Three P's were truly a law, then it would have to be true in every circumstance. And when we scan the entire U.S., we see many variations in the amount of intervention deemed "necessary" in womens' labors. Cesarean section rates vary from doctor to doctor, hospital to hospital. There is more prevelence of pitocin use in certain areas than others. Women at The Farm, Ina May's village in Tennessee, have consistently had a cesarean rate of less than 2%, while the rest of the country sees more and more cesareans each year, with a national rate of nearly 33%. How can this be if there was truth in the Law of the Three P's?

Even in Lawrence Impey’s textbook, Obstetrics and Gynaecology, right in the middle of discussing the Three P’s, he deviates away from his own writings by saying this:

"General Measures to Maintain Progress
Continuous support during labour is associated with a reduction in operative delivery and length of labor. This should be from the midwife, as well as partner, or from non-medical supporters or “doulas”. The impact of support is seldom remembered, but reflects the importance of psychological well being on obstetric outcomes. Mobility should also be encouraged."

It's very interesting to me to read in the middle of the formula for diagnosing dysfunctional labor, and how to correct them (artificial rupture of membranes, pitocin, then cesarean section), something so simple and so far removed from the medical/pharmacutical mindset. It also seems to counter what the Law of the Three P's deems to be true. That labors don't progress due to insufficient strength of the uterus, too large or malposition of baby, or too small inlet of the pelvis. How is the presence of a partner or doula making a uterus stronger, a baby smaller or better positioned, or the pelvis outlet bigger? While there are certainly things that a doula can do to help with these things, "psychological well being" is what is being pinpointed here. Isn't this what Sphincter Law concludes as well? That feeling loved, supported, protected and safe will help with labor progress?

So why are emotions so discounted in the obstetrical world? Or perhaps its not the emotions, but how to help a woman's emotions in labor that is being brushed aside. When administering pitocin is something that can be done quickly and checked on from time to time, staying with a laboring woman and supporting her seems like a big waste of time.

It just seems to me that obstetrics and hospitals function in a way that sets up a laboring woman to fail.

Information for this article came from

Birth, by Tina Cassidy

Ina May's Guide to Childbirth, by Ina May Gaskin

Obstetrics and Gynecology at a Glance, by Errol R. Norwitz and John O. Schorge

Obstetrics and Gynaecology, by Lawrence Impey