Your pelvic floor

Ever wonder why your pelvic and abdominal organs don't simply fall out? Probably not, but if you did stop to wonder about it, you might have concluded that it is the bones of the pelvis that keep everything inside. That's only part of the answer. In fact, the main structure that keeps everything inside is the pelvic floor.

The pelvic floor is the name for the group of muscles that overlap each other across the bottom of the pelvis. It acts like a hammock to suspend the pelvic organs and hold them in place. The pelvic floor looks like this:



Just like a hammock, it can become torn, stretched and worn. In fact, it can become so torn, stretch or worn that the pelvic organs do begin to fall out. That is known as prolapse.

What is prolapse? Why does it happen? How is it related to childbirth? And how do tears of the pelvic floor compare to and impact prolapse? To answer these questions, it helps to visualize the pelvic floor as a hammock made of spandex fabric, rather like the hammock in the photo above. Now imagine that the hammock has two small holes in it to let the rain flow and the leaves fall through. Two relatively small holes won't compromise the strength of the hammock.

What happens in pregnancy and childbirth? Pregnancy is the equivalent of a great weight on the hammock for a prolonged period of time. It is easy to see how that could stretch the hammock. Perhaps the fabric will return to its original shape and size, but if you leave the weight on the fabric long enough, or repeat the application of weight for long periods many times, the fabric will ultimately stretch and may not completely return to the previous shape. That's similar to the impact that pregnancy has on the pelvic floor.

How about childbirth? Imagine that a bowling ball is forced through one of the small holes in the hammock. A number of things may happen. The fabric may be stretchy enough to accommodate the bowling ball and to return to its original shape after the bowling ball passes through. It's also possible that the bowling ball will pass through, but the hole is permanently stretch. That's equivalent to a larger vaginal opening after childbirth. Finally, imagine that in order for the bowling ball to pass through, the fabric tears. That's the equivalent of a vaginal tear. The opening is now permanently larger. A small vaginal tear may heal on it's own, but if enough tissue is torn, it may not heal back together properly and the woman will be left with a gaping vagina.

A fourth degree vaginal tear is the equivalent of a tear in one hole of the hammock extending all the way into the second hole, leaving a big rent in the fabric. That will never heal by itself, and, it will leave the woman with bowel incontinence.

What about prolapse?

Prolapse is different but related.

Imagine that the hammock is used for the next twenty five years. It is almost inevitable that the fabric will get stretch and worn. The holes in the fabric, whether they are still in orignal shape, already permanently stretch, or actually torn, will widen still further. The same thing happens in the pelvic floor and the process accelerates as estrogen drops and disappears in menopause. Now the pelvic organs may begin to literally fall out.

When the bladder falls out (prolapses), it is called a cystocele. When the uterus false out it is known as uterine prolapse. Since the bladder is so close to the uterus, when the uterus falls out the bladder usually comes down with it. In either case, when the bladder begins to fall through the pelvic opening, women can lose control of their bladder. This kind of incontinence is known as stress urinary incontinence (SUI). Things are usually okay in most circumstances, but when a woman coughs, sneezes or laughs, intra-abdominal pressure is increased and the bladder is pushed through the opening in the pelvic floor and urine is forced out. Stress urinary incontinence is extremely common in women in their 50's and older.

If the rectum falls out, it is called a rectocele, and it can affect bowel continence.

What's the relationship between tears and prolapse? It's easy to envision that if the opening in the pelvic floor is already stretched or torn to larger than original dimensions, the stretch and wear of age is only going to make the problem worse. That's why vaginal birth puts a woman at much greater risk of prolapse. Having a C-section instead of a vaginal delivery does not guarantee that you will not ultimately develop a prolapse of one form or other. After all, simply being pregnant can permanent wear the muscles of the pelvic floor. However, vaginal delivery adds additional stretching, and possibly tearing to what would have happened anyway, making prolapse much more likely.

This explains the original impetus for episiotomy. Until the past few decades, there was not much that could be done for prolapse so doing anything possible to avoid it seemed like a good idea. The thinking behind episiotomy was to cut a straight "tear" before the muscles of the pelvic floor were stretched to their maximum and before they tore of their own accord. Unfortunately, in practice it did not work that way. Rather than protecting the muscles of the pelvic floor, the most common type of episiotomy (median episiotomy) actually made more extensive damage more likely. Hence the practice of episiotomy has been largely discarded. However, the idea was not a foolish one, and was worth trying.

Obviously this is a vastly simplified view of a complex anatomical issue, but hopefully it will help readers to better understand tears and prolapse, why they occur, and their ultimate consequences.