From the Catechism teaching on the fifth commandment:
2297 … Except when performed for strictly therapeutic medical reasons, directly intended amputations , mutilations , and sterilizations performed on innocent persons are against the moral law.
2322 From its conception, the child has the right to life. Direct abortion, that is, abortion willed as an end or as a means, is a “criminal” practice ( GS 27 § 3), gravely contrary to the moral law. The Church imposes the canonical penalty of excommunication for this crime against human life.
From the Catechism teaching on the sixth commandment:
2396 Among the sins gravely contrary to chastity are masturbation, fornication, pornography, and homosexual practices.
2399 The regulation of births represents one of the aspects of responsible fatherhood and motherhood. Legitimate intentions on the part of the spouses do not justify recourse to morally unacceptable means (for example, direct sterilization or contraception).
From the Catechism teaching on the ninth commandment:
2517 The heart is the seat of moral personality: "Out of the heart come evil thoughts, murder, adultery, fornication. . . . "305 The struggle against carnal covetousness entails purifying the heart and practicing temperance: …