Several historians argue that prior to the 19th century most Catholic authors did not regard termination of pregnancy before quickening or ensoulment as an abortion. Among these authors were the Doctors of the Church, such as St. Augustine, St. Thomas Aquinas, and St. Alphonsus Liguori. Pope Sixtus V (r.  1585–90) was the only Pope before Pope Pius IX (in his 1869 bull, Apostolicae Sedis) to institute a Church policy labeling all abortion as homicide and condemning abortion regardless of the stage of pregnancy. : 362–364 : 157–158  Sixtus V 1588 pronouncement was reversed in 1591 by Pope Gregory XIV. In the recodification of 1917 Code of Canon Law, Apostolicae Sedis was strengthened, in part to remove a possible reading that excluded excommunication of the mother. Statements made in the Catechism of the Catholic Church, the codified summary of the Churchs teachings, considers abortion from the moment of conception as homicide and called for the end of legal abortion.A 2014 Guttmacher survey of abortion patients in the United States found that many reported a religious affiliation: 24% were Catholic while 30% were Protestant. A 1995 survey reported that Catholic women are as likely as the general population to terminate a pregnancy, Protestants are less likely to do so, and evangelical Christians are the least likely to do so.
Woundings (e.g., Garson Romalis) and attempted murders have also taken place in the United States and Canada. Hundreds of bombings, arsons, acid attacks, invasions, and incidents of vandalism against abortion providers have occurred. Notable perpetrators of anti-abortion violence include Eric Robert Rudolph, Scott Roeder, Shelley Shannon, and Paul Jennings Hill, the first person to be executed in the United States for murdering an abortion provider.Legal protection of access to abortion has been brought into some countries where abortion is legal. These laws typically seek to protect abortion clinics from obstruction, vandalism, picketing, and other actions, or to protect women and employees of such facilities from threats and harassment. Far more common than physical violence is psychological pressure. In 2003, Chris Danze organized anti-abortion organizations throughout Texas to prevent the construction of a Planned Parenthood facility in Austin. The organizations released the personal information online of those involved with construction, sent them up to 1200 phone calls a day and contacted their churches. Some protestors record women entering clinics on camera. Non-human examples
Spontaneous abortion occurs in various animals. For example, in sheep it may be caused by stress or physical exertion, such as crowding through doors or being chased by dogs. In cows, abortion may be caused by contagious disease, such as brucellosis or Campylobacter, but can often be controlled by vaccination. Eating pine needles can also induce abortions in cows. Several plants, including broomweed, skunk cabbage, poison hemlock, and tree tobacco, are known to cause fetal deformities and abortion in cattle: 45–46  and in sheep and goats.