Rashi on Deuteronomy 22:22/רש"י על דברים כ״ב:כ״ב

1ומתו גם שניהם THEN THEY SHALL BOTH OF THEM DIE — The redundant words גם שניהם are intended to exclude a case of unnatural intercourse from which the woman derives no gratification (Sifrei Devarim 242:4; Sanhedrin 66b).

2גם is intended to include those persons who commit adultery with one of this pair after them (i.e. after this pair had been found guilty) (Sifrei Devarim 242:5). Another explanation of גם שניהם is: these words are intended to include in the death penalty the embryo: that if the woman was pregnant the execution is not deferred until after she gives birth (cf. Targum Jonathan on; Arakhin 7a).