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Birth Balance Blog

A series of topics related to preconception, pregnancy, labor, birth, bonding, and post partum issues. Feel free to make suggestions for future topics.

Pelvic Types

Pelvic Evaluation:

Let’s talk about the pelvis (as it relates to women). In general, the
 pelvis consists of four bones (paired innominate bones, coccyx, and
 the sacrum) held together by ligaments. The size and shape of
 these bones have a tremendous impact on how a woman looks
 physically. Medically speaking, pelvic shape is classified using
 something called the “Caldwell-Moloy” system.
There are four basic pelvic shapes:

Gynecoid     •     Android

Anthropoid   •      Platypoid

A gynecoid pelvis is oval at the inlet, has a generous capacity and wide subpubic arch. This is the classical female pelvis. Pelvic brim is a transverse ellipse (nearly a circle) Most favorable for delivery.The gynecoid pelvis (sometimes called a “true female pelvis”) is  found in about 50% of the women in America. It is the “classic” form that we associate with women and has an anteroposterior diameter  just slightly less than the transverse diameter. Lucy Lawless of Xena, Warrior Princess fame has a classic gynecoid pelvis. Women like this tend to look…like women. They are shapely and curvy. They tend to hold fat around the thighs more so than the mid-riff. They can have a flat stomach without                                                        really dropping body fat levels low enough to cause some “female problems.”

A platypoid pelvis is flattened at the inlet and has a prominent sacrum. The subpubic arch is generally wide but the ischial spines are prominent. This pelvis favors transverse presentations.  Pelvic brim is transversekidney shape. The platypelloid pelvis is very short (almost like a “flattened gynecoid shape”). Only about 3% of women have a true and pure pelvis of this type. Women having a platypelloid pelvis tend to carry a lot of weight in the lower abdomen. It’s very difficult for these women to have really flat abdomens without getting body fat levels down into the                                                                              single digits.

Flattened gynecoid shape

An anthropoid pelvis is, like the gynecoid pelvis, basically oval at the inlet, but the long axis is oriented vertically rather than side to side.Subpubic arch may be slightly narrowed. This pelvis favors occiput posterior presentations.  Pelvic brim is an anteroposterior ellipse, Gynecoid pelvis turned 90 degrees, Narrow ischial spines.  Much more common in black womenThe anthropoid pelvis is very long and almost “ovoid” in shape. It is more common in non-white females (it makes up about 25% of pelvic type in white women and close to 50% in non-white women). Women who have such a pelvis shape tend to have “larger rear ends” and may carry a lot of adipose tissue/weight in the buttocks as well as in the abdomen. These women can have a flat stomach with some real effort (they may have to drop body fat levels down a bit lower than women with the other two aforementioned pelvis types, but it’s “doable”).

 

An android pelvis is more triangular in shape at the inlet, with a narrowed subpubic arch. Larger babies have difficulty traversing this pelvis as the normal areas for fetal rotation and extension are blocked by boney prominences. Smaller babies still squeeze through. (Male type)  Pelvic brim is triangular  Convergent Side Walls (widest posteriorly)  Prominent ischial spines,  Narrow subpubic arch, More common in white womenThe android pelvis (sometimes called a “true make pelvis”) is found in about 20% of American women. Women who happen to have such a pelvis tend to have “flat rear ends.” Many of the truly “waifish women” we see so prominently in modeling today have this type of pelvis. It’s not necessarily a good thing for a woman to have such a pelvic shape, as most of these women will end up having a Cesarean Section if they want to have children. Women with this shape of pelvis have virtually no real difficulty in achieving a flat stomach—no more than the “average male”—because their pelvises are shaped like an average male.

PELVIC INLETS:

GYNECOIDPLATYPOIDANTHROPOIDANDROID

  1. Caldwell-Moloy Classification
    1. Gynecoid Pelvis (50%)
      1. Pelvic brim is a transverse ellipse (nearly a circle)
      2. Most favorable for delivery
    2. Android Pelvis (Male type)
      1. Pelvic brim is triangular
      2. Convergent Side Walls (widest posteriorly)
      3. Prominent ischial spines
      4. Narrow subpubic arch
      5. More common in white women
    3. Anthropoid Pelvis
      1. Pelvic brim is an anteroposterior ellipse
        1. Gynecoid pelvis turned 90 degrees
      2. Narrow ischial spines
      3. Much more common in black women
    4. Platypelloid Pelvis (3%)
      1. Pelvic brim is transverse kidney shape
      2. Flattened gynecoid shape

 

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