Pelvic Bones: The Importance of Childbearing Hips
Last but not least, your pelvic shape. What could be more basic to the way a baby travels through your pelvis? The width, depth, and space between your pelvic bones have important effects not only on how fast labor progresses but also on what types and how much pelvic injury might occur during childbirth. Yet you’ve probably heard very little about this aspect of your body and how it can influence childbirth decisions.
Through your obstetrician’s eyes, your pelvis has an inlet, an outlet, and in between, a midpelvis. Though every woman has her own unique pelvic shape, four classic shapes identified in the 1930s are still used to describe your bony pelvic shape, and to predict—though not always very reliably—the way it might affect the course of your childbirth. Your doctor can determine your pelvic shape by taking a series of measurements during a regular pelvic examination (called pelvimetry). Unfortunately, it’s not possible to guess your pelvic shape based on outward appearance.
Gynecoid
This is the most common female pelvic shape, found in around 30 percent of women. Fortunately, it is the one most suited for a successful childbirth. The gynecoid pelvis has relatively plentiful space in all areas—front, back, and sides. Its front pubic bones are fairly open and wide, and the spines of the pelvis (a knob of bone located on either side of the pelvis’s inner wall) don’t protrude very far into the birth canal. So if you have a gynecoid pelvis, take a moment to thank your parents: they’ve handed down some good childbearing genes!
Android
This pelvic shape with the Star Wars name can present problems for vaginal delivery. Much like the typical male pelvis (andro means man), the front arch of the pubic bones is narrower than the gynecoid shape, and the spines on the pelvic sides tend to jut into the birth canal, shrinking the passageway for the fetal head. In the rear, the tailbone and lower spine (sacrum) also protrude forward, closing off precious space. Overall, these features create a narrow heart shape, relatively small at both the inlet and outlet, making a difficult delivery more likely. Although fewer than 5 percent of women are thought to have a pure android shape, many women have mixed pelvic shapes, including both android and gynecoid features.
Anthropoid
This pelvic shape, seen in fewer than 15 percent of women, is a thin oval. The spines on the pelvic walls are often large, leaving relatively little side-to-side space for the fetus during delivery.
Platypelloid
This is the least common pelvic shape, resembling an oval tipped on its side. Some experts claim that women with a platypelloid pelvis are at significantly higher risk for incontinence and prolapse, as well as recurrent prolapse after surgery has been performed, due to the pelvic organs and supports being more exposed and vulnerable to the trauma of childbirth and also the forces of gravity. An interesting hypothesis, but one that has yet to be scientifically tested.
What's Your Pelvic Shape?
Whatever the shape of your pelvic bones, they’re important to your postreproductive health. They can impact childbirth’s physical ease or difficulty, the way your baby travels through the birth canal, and the amount of pressure, stretch, and potential injury to each area along the way. That, in turn, has an impact on the problems you’re at risk for afterward.
Consider the shape of your pubic arch, formed by the bones that you can feel for yourself at the front of your pelvis, below your pubic hairline. If the pubic arch is narrow (android or anthropoid), that means less room for the fetus in the front of your pelvis. As a result, a large fetal head or wide shoulders may be more likely to stretch and tear downward, into the perineum and rectum, during delivery. If, on the other hand, you have a wide pubic arch (gynecoid, platypelloid), or a tailbone that angles forward, the fetal head might tend to be pushed up toward the pubic bone, directly into the bladder and urethra. What if the bones are narrow along the sides of your pelvis, creating pressure points between the fetal head and the pudendal nerve running along each pelvic side wall? Consider how much more force might be applied to those nerves in a narrow anthropoid pelvis, compared with a wide gynecoid one.
Conclusion
While a great deal remains to be learned about how pelvic shape may influence the effects of vaginal delivery on your postreproductive body, the anatomy of the female pelvis plays a crucial role in childbirth and postreproductive health. Connective tissues and ligaments provide support to pelvic organs, though surgical repairs often rely on grafts when these structures weaken. Pelvic bone shape is equally significant, with four classic pelvic shapes—gynecoid, android, anthropoid, and platypelloid—affecting the ease of delivery and the likelihood of complications. Gynecoid, the most common and favorable shape for childbirth, provides ample space for the baby’s passage, while narrower shapes like android and anthropoid can lead to more difficult deliveries. Understanding the differences in pelvic shapes allows both women and healthcare providers to make more informed decisions during pregnancy and childbirth, tailoring care to individual needs for better outcomes.
Coming Up in Part 3: Your Pelvis During Pregnancy and Delivery
In the next section, we'll explore the fascinating changes that occur in the pelvis during pregnancy, from the thickening of vaginal walls to the hormonal softening of pelvic joints, all working together to prepare for delivery. You'll also learn about the concept of fetal engagement—what it means when the baby's head "drops" into the pelvis—and how this can influence your delivery experience. As we continue, we'll examine how labor stages put intense pressure on the pelvis, and why understanding these changes can make all the difference in a successful birth. Stay tuned to discover more about how your body adapts to one of life's greatest challenges!
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