Understanding Cephalopelvic Disproportion

So what is CPD? With the majority of primary cesareans being due to the diagnosis of CPD, it might be wise for women to have a healthy understanding of what true CPD is. The medical definition of true CDP is a combination of arrested cervical dilation after five centimeters dilation and unresponsiveness to oxytocin augmentation after active dilation, of more than two centimeters, in two hours. Therefore, CPD is really a diagnosis of failure to progress (FTP).

True causes of CPD include medical indications as to why the baby is too big (such as Hydrocephalus) or why the woman's pelvis is too small (such as malnutrition, pelvic fracture, or rickets). Obese women and women small in stature are more likely to be diagnosed with CPD, though both delivery vaginally all the time.

It is very important to remember that each baby and pregnancy are unique, so a woman who has her first child by cesarean section due to CPD has a very good chance of being able to deliver subsequent children vaginally. Take for example, a study by the National Maternity Hospital and University College of Dublin, Ireland¹. This study examined 42,793 women and found only 84 (.002%) who had true CPD. Of the 84, 40 women participated in the study's trial of labor for subsequent births. Of the 40, 68% gave birth vaginally. Their conclusion: "The strictly defined diagnosis of nulliparous cephalopelvic disproportion should not constitute an automatic "recurrent" indication for cesarean delivery". Other studies have found similar results.

What is required for a birth to work optimally? A collective opinion of experienced birth professionals conclude that the following guidelines must be met in labor or a difficult birth is more likely to occur:
* Being upright
* Maintaining privacy
* Being on baby's time instead of the hospital's time
* Not receiving painkillers
* Not being subjected to continuous fetal monitoring
* Reducing the use of Pitocin and other labor inducing/augmenting drugs
* Being aware of the baby's position and presentation
* Letting labor start on its own
* Being allowed to rest, eat food and drink fluids
and perhaps most importantly,
* Have a support system who truly believes women are able to give birth, and who are willing to lend encouragement and strength to the birthing woman

I love what Ina May Gaskin has to offer women who were previously sectioned for CPD. She tells them that, "they will get big, bigger than the baby. And it works ... women are not limited. Mothers get bigger than the baby"². Women are built to have babies. Their bodies release a significant amount of the hormone, Relaxin, after 34 weeks of pregnancy. This helps their pelvis to loosen up and make way for the child in her pelvis. At the time of labor and birth, the pelvis open at three different points, adn the four cranial bones in the baby's head overlap, so that the baby is able to travel down and out the birth canal.

Perhaps the best way to encourage women is to share firsthand stories of women who defied the odds that our society has built around them, and gave birth vaginally:

Laura, who is small in stature, was sectioned with her first baby (9lbs 14oz) and diagnosed with CPD. She gave birth vaginally to her second child (11lbs) after a four hour labor with no tearing.

Lisa, who is 4'8" tall, was told by her medical caregivers that her chance of a VBAC with her second child was only 30%, so she searched out midwives to support her, and she gave birth at home with only a half hour of pushing.

"Sarah", would almost certainly have been diagnosed with CPD if she had delivered at a hospital. She was so small in stature that she wore size two shoes. Instead she found a supportive midwife and gave birth to her 7lb daughter in a watertub at home.

There are cultures around the world where CPD is the rare phenomenon that it should be. One study showed that women in the United States were six times more likly to be diagnosed with CPD than women in Ireland. In Africa, Pygmy women (who average 4' tall) give birth to babies who average 8lbs. That is like a 5'6" woman giving birth to a 14lb baby!

If you have been diagnosed in the past with CPD adn are facing another birth, I encourage you to challange the system and to believe in yourself. Find a supportive care provider who sees you as a strong experienced woman, not as a disproportionate pelvis. There are times when true CPD prevents women from giving birth vaginally, but in most cases, the next birth will be completely different. Remember, you have at least a 68% chance of attaining a vaginal birth.

Sources:
1 - Obstet. Gynecol., 92(5): 799-803. Nov 1998
2 - Birthing From Within by England and Horowitz