The fundamental nature of the marriage act, while uniting husband and wife in the closest intimacy, also renders them capable of generating new life—and this as a result of laws written into the actual nature of man and of woman. And if each of these essential qualities, the unitive and the procreative, is preserved, the use of marriage fully retains its sense of true mutual love and its ordination to the supreme responsibility of parenthood to which man is called.” (Humanae Vitae, Encyclical Letter, Pope Paul VI, No. 12)

“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).” (CCC, No. 2399)

ABORTIFACIENTS AND  CONTRACEPTION

Catechism of the Catholic Church
# 2370, 2399

Humanae Vitae (1968)
Encyclical Letter of Pope Paul VI on the regulation of birth

A Study Guide to Humanae Vitae
Written by the Priests and Pastoral Associates of Priests for Life

Casti Connubi (1930)
Encyclical letter of Pope Pius XI on Chrisian marriage, stressed the sanctity of marriage, prohibited the use of any form of artificial birth control, and reaffirmed the prohibition on abortion

The Contraception of Grief
The Genesis of Anguish Conceived by Abortifacients and Sterilization by Theresa Burke

The Difference between artificial birth control and natural family planning
Couple of Couple League, an international Catholic organization dedicated to fertility awareness education

The Pill – How It Works and Fails
Q & A from Pharmacists for Life International

How Do the Pill and Other Contraceptives Work?
Q & A with Dr. Chris Kahlenborn specializes in internal medicine and practices in Altoona, Pennsylvania.

The Birth Control Pill: Abortifacient and Contraceptive
William F. Colliton, Jr. M.D.