## **Core Concept**
The question pertains to the anatomical dimensions of the pelvis, specifically focusing on the planes of the pelvis and their measurements. In obstetrics and gynecology, understanding the pelvic dimensions is crucial for assessing the feasibility of vaginal delivery. The pelvis can be divided into several planes, each with distinct measurements.

## **Why the Correct Answer is Right**
The correct answer, , refers to the plane of least pelvic dimension, also known as the interspinous diameter or the plane of the ischial spines. This plane typically measures approximately 10 cm in anteroposterior diameter and 12 cm in transverse diameter. It represents the narrowest part of the pelvic cavity in the anteroposterior dimension and is a critical measurement in obstetrics.

## **Why Each Wrong Option is Incorrect**
- **Option A:** - This option does not accurately represent the plane of least pelvic dimension. The plane of the pelvic inlet has a larger anteroposterior diameter compared to the interspinous plane.
- **Option B:** - This option refers to another plane within the pelvis but not the one with the least dimension.
- **Option D:** - Similarly, this option does not accurately describe the plane with the least pelvic dimension.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the interspinous diameter (or the plane of the ischial spines) is typically the narrowest diameter of the pelvis in the anteroposterior dimension, measuring about 10 cm. This measurement is critical in obstetrics as it can influence the progress of labor and the feasibility of vaginal delivery.

## **Correct Answer:** .