This animation displays the sagittal view of a pregnant female's uterus and the mechanism of shoulder dystocia during delivery. The baby starts in the occiput anterior (OA) position and its head turns as it passes through the pelvic inlet. The baby's head then returns to the original position as it passes through the midpelvis. Next, the baby's shoulders turn vertical as they prepare to pass through the midpelvis, twisting the head to 90 degrees. As the head is delivered, the shoulder is directly behind the pubic bone, causing shoulder dystocia and injury to the brachial plexus of the fetus. Maternal anatomy highlighted in this animation includes the uterus, pubic symphysis, coccyx, and sacrum.
