Pelvic brim

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The pelvic brim is an important anatomical landmark in the human pelvis. It is the edge of the pelvic inlet, which is the upper opening of the true pelvis. The pelvic brim separates the false pelvis (above) from the true pelvis (below).

Anatomy

The pelvic brim is formed by the following structures:

• The sacral promontory and the ala of the sacrum posteriorly.
• The arcuate line of the ilium laterally.
• The pectineal line and the pubic crest anteriorly.

Clinical significance

The pelvic brim is a critical landmark in obstetrics. It is used to assess the size and shape of the pelvis, which is important for determining the mode of delivery during childbirth. A pelvis that is too small or has an abnormal shape can lead to complications during labor and delivery.

Pelvic types

The shape of the pelvic brim can vary among individuals and is classified into four main types:

• Gynecoid pelvis: The most common type, which is round and wide, facilitating childbirth.
• Android pelvis: Heart-shaped and more common in males, can pose challenges during childbirth.
• Anthropoid pelvis: Oval-shaped and elongated, generally favorable for childbirth.
• Platypelloid pelvis: Flat and wide, can make vaginal delivery difficult.

Related structures

• Pelvic inlet
• Pelvic outlet
• Pelvic cavity
• Pelvic floor

See also

• Pelvis
• Obstetrics
• Labor (childbirth)
• Anatomy

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