Which of the following pelvic diameter measures the distance from the lower margin of the symphysis to the sacral promontory?
Diagonal conjugate diameter is determined by measuring the distance from the lower margin of the symphysis to the sacral promontory. Obstetric conjugate is the shoest distance between the promontory of the sacrum and the symphysis pubis. It is usually calculated by subtracting 1.5 to 2 cm from the diagonal conjugate. Normally, this measures 10 cm or more. The transverse diameter is at right angles to the obstetrical conjugate and it represents the greatest distance between the linea terminalis on either side. It is usually 13cm in diameter. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 2. Maternal Anatomy.
Transverse diameter
Diagonal conjugate
Obstetric conjugate
True conjugate diameter