As a ban on a procedure that opponents call partial-birth abortion makes its way through Congress, many of the doctors who provide abortions say they remain confused about what will be banned and fear it will apply to other procedures used in the second trimester of pregnancy. The procedure at issue — what doctors now call intact dilatation and extraction, or intact D&X — involves pulling the fetus's legs and torso out of the uterus and then crushing its skull before removing it entirely. It is not known how often it is performed in the United States, but its use...