Some medical conditions can be made worse by becoming pregnant. Pulmonary hypertension, for example, is often exacerbated by pregnancy: the additional blood volume of the pregnancy burdens the mother's weakened heart and, in extreme cases, can result in heart failure and the death of both mother and child.

Although direct abortion is sometimes counseled to pregnant women who face this life-threatening difficulty, such a choice can never be moral. In these circumstances, medical strategies which seek to care for both mother and child need to be pursued, as they often provide satisfactory outcomes for both.

Recent advances in obstetrics and pre-natal medicine, along with so-called "expectant management" (close monitoring of a pregnancy with tailored interventions), have enabled an ever greater number of these high-risk pregnancies to be managed at least until the child reaches viability. Labor can then be induced or a C-section delivery can be scheduled. This ordinarily allows both mother and child to be saved.

An April 2010 research study showed impressive survival rates for pregnant mothers with pulmonary hypertension. This was achieved by combining multi-specialty collaboration with planned and managed delivery. The results, published in the British Journal of Obstetrics and Gynecology (BJOG), indicated that all nine of the patients in the small study group survived along with their unborn children.

Nevertheless, there are times when our best medical efforts to save both mother and child will fail, and we face the heart-wrenching situation where nature may have to take its course. In these circumstances, some ask: Wouldn't a direct abortion be permissible to save the mother (for example, a suction curettage procedure, a common form of abortion where the fetus is often dismembered and parts are evacuated from the uterus)?

An analogy can help us grasp the unacceptability of direct abortion in a situation like this.

Let's suppose that several firefighters enter a burning building to evacuate a child trapped on the third floor. The firefighters discover that part of the building has collapsed onto the only stairwell, with heavy, immobile concrete girders blocking the passageway further up to the landing. There is only a small hole in the girders that the firefighters would need to crawl through to get to the trapped child, but the passage is blocked by the body of a man who collapsed from smoke inhalation right in the crawl space where the firefighters need to go. He is wedged in there in such a way that his unconscious, but living, body cannot be moved aside or out of the way.

As the fire pulses dangerously around them, it becomes apparent that the only way the firefighters might be able to quickly pass would be to take a saw and cut the body of the collapsed man into pieces, causing his death, and then pull out sections of his body until a passage large enough for them to pass through had been opened up. Clearly, the firefighters would be obligated to try everything else to save the child and the collapsed man (shifting his body this way or that, trying to rouse him from his unconsciousness, etc.) but they could never choose to directly kill him by cutting up his body, even for the very good reason of gaining access to the next floor and saving the trapped child.

This example points towards an old adage sometimes cited by moralists: Better two deaths than one murder. Some might say that "murder" would not fit here, given that the term generally connotes a callous, wanton, and premeditated act of killing, instead of an urgent, emotional and difficult decision in the face of few or no alternatives. But even the strongest emotion and the greatest difficulties surrounding such cases must be focused through the lens of a similar affirmation: Better two deaths than the direct taking of an innocent life.

Directly killing an innocent human being, even in the hopes of saving his or her mother, is an instance of engaging in an intrinsic -- or absolute -- evil, even if good may follow. By always repudiating the direct killing of the innocent, and acknowledging that this represents an exceptionless norm, we set in place the framework to safeguard human dignity at its root. Affirming this most basic norm leads us away from the injustice of playing God with other people's lives. These challenging "life of the mother" cases allow us to begin acknowledging some of our own limitations, and the mystery of God's greater Providence, in the realization that we may not be able to "manage" or "correct" every difficult medical situation we face.

Father Tadeusz Pacholczyk, Ph.D. earned his doctorate in neuroscience from Yale and did post-doctoral work at Harvard. He is a priest of the diocese of Fall River and serves as the Director of Education at The National Catholic Bioethics Center in Philadelphia.