Catechism of the Catholic Church §2272 — excerpt
Formal cooperation in an abortion constitutes a grave offense. The Church attaches the canonical penalty of excommunication to this crime against human life. "A person who procures a completed abortion incurs excommunication latae sententiae," "by the very commission of the offense," and subject to the conditions provided by Canon Law.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: CIC, can. 1398 · CIC, can. 1314 · CIC, cann. 1323-1324