Under a 1988 Vatican ruling, "abortion" is defined as any method used to terminate a pregnancy from the moment of conception. Abortion thus understood is always illicit, according to the official discipline of the Catholic church, and can trigger excommunication for the parties involved.

The church's condemnation of abortion includes not only interventions to remove a fetus before birth, but the use of all abortifacients, including intrauterine devices and certain types of birth control pills that prevent implantation or stimulate uterine contractions to reject a fertilized egg. It also encompasses drugs such as RU486, called the abortion pill, which provokes miscarriages by blocking progesterone in the first weeks of pregnancy.

This expansive standard is expressed in a May 23, 1988, ruling from the Pontifical Council for the Interpretation of Legislative Texts, the Vatican office charged with authoritative interpretations of canon law. The council was responding to a dubium, or request for clan ification, from a bishop on canon 1398, which stipulates excommunication as the penalty for abortion.

The ban on abortion, in the sense of the deliberate termination of a pregnancy, is absolute.

According to Redemptorist Fr. Brian Johnstone, a bioethics expert at Rome's prestigious Alphonsian Academy, the lone situation in which the removal of a fetus may be tolerated by official Catholic teaching is if the mother urgently requires a life-or-death procedure with the unwanted consequence of ending her pregnancy. A pregnant woman with advanced-cervical cancer, for example, could have an operation to remove the cancer, which would also mean removing the fetus. In Catholic moral theology, this is understood as the principle of "double effect." The positive effect, saving the life of the mother, is what is intended, while the negative effect, the death of the fetus, is merely foresee.

There are recent cases in Italy, Johnstone said, in which women in similar circumstances have chosen to continue with their pregnancies. In some of these cases, he said, the child was born healthy while the mother died. The church admires such sacrifice, Johnstone said, but it does not oblige anyone to make this choice.

While the deliberate removal of a fetus has always been banned, Johnstone said, historically there has been debate among Catholic theologians as to whether all such acts qualify as "abortion," in the sense of homicide, or whether termination of pregnancy at an early stage is more akin to contraception.

St. Augustine wrote in the fourth century that abortion could be viewed as murder only if the fetus was judged a "fully formed" human. That stage of development, "hominization," occurred for Augustine some time after conception - 40 days for males and 80 days for females. St. Thomas Aquinas, the 13th-century Dominican theologian, likewise held that "infusion" of the human soul took place between 40 and 80 days after conception, following the biological views of the Greek philosopher Aristotle.

The interruption of a pregnancy prior to this point was for Augustine, Aquinas and those who followed them, Johnstone said, a particularly grave form of birth control rather than abortion.

This tradition held until Pope Sixtus V, a Franciscan and reformer of moral standards in the Papal States, who in 1588 decreed excommunication for any termination of a pregnancy from the moment of conception. His motive, according to Johnstone, was to crack down on prostitution in Rome. The campaign was a failure, and three years later Gregory XIV reversed the edict. Finally, in 1869, Pope Pius IX sidestepped the ho- minization debate and declared that the fetus, "although not ensouled, is directed to the forming of man. Therefore, its ejection is anticipated homicide" at any stage of pregnancy and incurs excommunication.

Johnstone stressed that there was never any question of whether terminating a pregnancy was sinful, but rather what kind of sin it was in the early stages - homicide or something else. Hence it would be inaccurate to say that the church ever "permitted" abortion.

Today, Canon 1398 of the 1983 revision of the Code of Canon Law reads: "A person who actually procures an abortion incurs a latae sententiae excommunication." The word "actually" indicates that the abortion must have been successful for the penalty to occur; the mere intent to have an abortion is not sufficient.

That the penalty is latae sententiae means it is automatic, and hence there is no need for an official decree. Most excommunications, by way of contrast, have to be proclaimed by church authorities in order to take effect; these are called feren- dae sententiae. There are seven acts in canon law that trigger latae sententiae excommunication. Aside from abortion, they are: violence against the pope; sacrilege such as throwing away a consecrated host; absolving a person with whom one has sinned against the sixth commandment; consecrating a bishop without authorization; violating the seal of confession; and apostasy, heresy or schism.