North American Registry of Midwives (NARM) Practice Exam

Which type of pelvic shape is characterized by a wide public arch that can complicate fetal descent during birth?

1. Anthropoid

2. Platypelloid

3. Gynecoid

4. Android

The correct answer is: Platypelloid

The platypelloid pelvic shape is characterized by a wide pubic arch, which can indeed complicate fetal descent during labor. This particular pelvic type has a flat transverse diameter and a broader pubic inlet, leading to challenges when the fetus attempts to navigate through the birth canal. The increased width of the pubic arch can create a less favorable angle for the fetal head to engage and descend through the pelvis. While the other pelvic shapes also influence labor, they do not possess the same combination of features that specifically complicates fetal descent as seen in platypelloid pelvises. For example, the gynecoid pelvis, often considered the most favorable shape for childbirth, has a rounder inlet and a better capacity for fetal passage. Android and anthropoid pelvises, while having their own characteristics and potential complications, do not feature the same wide pubic arch that defines the platypelloid shape. Understanding the nuances of pelvic shapes helps midwives anticipate potential challenges during labor and assists in planning appropriate care strategies.