The smallest anteroposterior diameter of the pelvic inlet is called the
A. Interspinous diameterB. True conjugate
C. Diagonal conjugate
D. Obstetric conjugate
The answer is d.
The obstetric conjugate is the shortest distance between the promontory of the sacrum and the symphysis pubis. It generally measures 10.5 cm. Because the obstetric conjugate cannot be clinically measured, it is estimated by subtracting 1.5 to 2 cm from the diagonal conjugate, which is the distance from the lower margin of the symphysis to the sacral promontory. The true conjugate is measured from the top of the symphysis to the sacral promontory. The interspinous diameter is the transverse measurement of the midplane and generally is the smallest diameter of the pelvis.
