Roman Catholic teaching on life and death is drawing renewed scrutiny as a result of meetings hosted by the Pontifical Academy for Life, a Vatican think tank that counsels Pope John Paul II.
The academy, after a conference on assisted fertility, condemned treatments such as in-vitro fertilization, calling the destruction of embryos in the process a "massacre of the innocents."
And at another conference last month, John Paul said removing feeding tubes from people in persistent vegetative states was immoral, and that no judgment on their quality of life could justify such "euthanasia by omission."
Church leaders say they are not opposed to medical advances, but want to ensure that any procedures used are moral, preserve human dignity and - in the case of reproductive technology - protect the sanctity of the "conjugal act" between husband and wife.
But some non-Catholics in medicine, along with a few Catholic theologians, are warning that the church's positions - which can influence legislation, medical regulations and research - risk curtailing medical progress and are not always in the best interests of patients.
The communique the academy issued after its fertility conference restated positions in the 1987 document on reproduction known as Donum Vitae, or Gift of Life, from the Congregation for the Doctrine of the Faith, the Vatican's orthodoxy watchdog.
The academy said that any treatment that substitutes for sex between a husband and wife is illicit because the embryo isn't the fruit of the "conjugal union." However, medical therapies are permitted that "facilitate" reproduction through sex between a husband and wife, the academy said. No examples were cited, but many Catholic theologians agree that fertility drugs and surgery to overcome tubal blockages are allowed.
Catholic bioethicists mentioned another option - using condoms - despite the church ban on artificial contraception. They said a condom, if perforated, could be used to collect semen during sex for later use in a medical insemination procedure without violating church teaching.
Some medical ethicists say the church is out of touch with treatments that are accepted and embraced in many countries - including largely Roman Catholic Italy, which recently passed legislation that greatly restricts fertility treatments but still allows for limited in-vitro fertilization.
As a result, they warn that countries that limit such treatments risk being left behind as stem-cell research progresses_ a fate that is increasingly evident in Europe, said Dr. Arne Sunde, chairman of the European Society for Human Reproduction and Embryology.
If researchers in one country discovered an embryonic stem-call cure for paralysis, for example, "wouldn't it be tough to say this isn't for Catholics," Sunde said in a phone interview.
"Reproduction is one thing," he said. "But there's another issue when people are about to die and you can't save them."
The academy's conference on end of life issues focused on persistent vegetative states, where patients seem to be awake but are not aware of themselves or their environment.
John Paul said that it was immoral to withdraw food and water tubes from such patients since they would die. He called feeding tubes normal care, not extraordinary medical treatment - a distinction he said made them obligatory to use until they no longer benefited the patient.
Not all Catholic theologians agree.
The Rev. Kevin O'Rourke, founder of the Center for Health Care Ethics at St. Louis University, argued in a 2001 article that remaining in a vegetative state is of no real benefit to patients because they cannot strive for the purpose of life, which the church has defined as pursuing a "friendship with God."
If a patient doesn't have the cognitive function to know and love, he or she can't pursue that friendship, and therefore treatment has no benefit, O'Rourke says.
O'Rourke's argument was criticized during the conference - attended largely by Catholic doctors and prelates - as were recent court cases in the United States which have endorsed patients' advance directives instructing doctors to withdraw feeding tubes.
Dr. Eugene Diamond, director of the Linacre Institute of the Catholic Medical Association and a conference speaker, said courts had "made us killers in the abortion decision, now they're trying to make us the killers at the other end of life."
The trend in medical ethics is to heed patients or their proxies, although a line is drawn when it comes to assisted suicide, said Dr. Michael Goldrich, the chairman of the American Medical Association's Council on Ethical and Judicial Affairs, who did not participate in the conference.
"There's a big difference between relieving pain ... and the purposeful acceleration of death," he said in a phone interview. "We recognize that sometimes as a consequence of relieving pain that an individual can be accelerated toward death, and that's viewed as an acceptable end of life alternative."