Probably the most common conflict (and it is surprisingly rare) is taking care of the client requiring an abortion or having post-AB complications. Since most AB's take place in outpatient settings, it's not that big of a deal. Nurses that hire on in those situations have decided that the ethics are comfortable for them. Catholics may also not want to do care of tubal ligation patients, IUD patients etc. I am Catholic and due to my personal ethics, I would not prefer to work in a clinical setting offering abortions. In my old nursing school setting, we simply could opt out of a clinical situation that offered us conflicts (the rare AB).
BTW, many Catholic docs and nurses do not feel conflicted by caring for contraceptive clients. I worked in a Title X (contraception) clinic for several years and did not feel that conflicted, though some nurses I know definitely would. On the other hand, some docs (both Catholic and other faiths), will not order cotraceptives for their unmarried female clients, but they are usually willing to refer patients to a doctor that will. Actually, my ethics are significantly offended by women who have children outside of the context of a stable relationship, but I don't feel the need to tell the patient this so the conflict mainly occurs within me. Ultimately, I was more comfortable with the prevention of pregnancy than intervening in high risk, teen families.
Technically, the church frowns upon IVF and artificial insemination, I believe. I guess nurses that work in those fields have to find that comfort level with what they are doing if they happen to be Catholic.
Again, most end of life care offends me not because it prematurely terminates life, but because the patients are endlessly drug through the knot-hole of one more medical intervention. Conversations with a priest will likely reassure you on this point. The church does not require families to needlessly prolong a life when their is no hope of meaningful existence. One of my former clients was a vent dependent child with a very poor quality of life and his Catholic parents were endlessly reassured by priests that the church did not require them to continue what they were doing. They did elect to continue it however. This is not too atypical. it is often the family that opts to continue to fight the good fight.
Catholics and religiously/spiritually motivated nurses often (but not always) make good nurses. I guess in general a religious or spiritual tradition that helps you to be patient and to understand that suffering is sometimes part of life simply helps you to cope with what it is you see. At the same time, weekend shifts, weird hours eroded my affiliation with my church. I often went to church to be present in body but not mind or soul. It was hard to be part of a church. Weekends were so precious that sometimes you didn't go to the church event; you did something else. Now that I don't work shifts, I find myself rediscovering my church.
Also had a (not Catholic) nurse colleague who would try to "convert" ventilator dependent people in my ICU over a decade ago. This was a source of chagrin to all of us and simply not appropriate.
Nursing teaches you to be sensitive to a lot of different traditions and really can broaden your own spirituality.
By no means are the ethical dilemma insurmountable.