Diagonal conjugate is:

Ans. B. Lower border of symphysis and sacral promontoryDiagonal conjugate is distance between lower borders of symphysis pubis to the midpoint on sacral promontory. It measures 12cm. it is measured clinically during pelvic assessment in late pregnancy or in labor. Obstetric conjugate is computed by subtracting 1.5 to 2cm from diagonal conjugate. True conjugate is inferred by subtracting 1.2cm from the diagonal conjugate.