Mechanisms of Labor

Step by step

The Maternal Pelvis


During childbirth the fetus has to pass through the maternal pelvis. At the pelvic inlet it has an oval shape with its transverse diameter (13 cm) wider than its anteroposterior diameter (11 cm).

The pelvic outlet is anteroposterior ovally shaped with a transverse diameter of 11 cm and an anteroposterior diameter of approximately 11,5cm.

At the pelvic inlet the orientation of the birth canal is cranial to caudal. While at the level of the pelvic outlet it is dorsal to ventral. Fetal descent through the pelvis is therefore via a 90 degree angle, shown here by the pelvic axis. An imaginary line trough the center of the pelvic inlet, cavity and outlet.

Do you want to learn the complete step-by-step of "Mechanisms of Labor"?

Try one of our offerings


Unlock your free Incision procedure


Unlimited access to all 374 procedures.

20 per month Get started