Dr. Warren Hern, late term abortionist, describes a D&E procedure in this book Abortion Practice:
“As the calvaria [head] is grasped, a sensation that it is collapsing is almost always accompanied by the extrusion of white cerebral material [the brain] from the external os. this calvaria sign may not be much in evidence with the 13-week procedure, but it is more likely to appear at 14 weeks. Prior to 14 weeks, the calvaria may enter the suction cannula and may not be noticed.”
Warren Hern Abortion Practice (Boulder, CO: Alpengo Graphics, INC, 1990) p 142