The procedure changes significantly at 21 weeks because the fetal tissues become much more cohesive and difficult to dismember. This problem is accentuated by the fact that the fetal pelvis may be as much as 5 cm in width. The calvaria [head] is no longer the principal problem; it can be collapsed. Other structures, such as the pelvis, present more difficulty… A long curved Mayo scissors may be necessary to decapitate and dismember the fetus…
— Warren Hern, late-term abortionist
