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.
