27 Likewise we hold in the highest esteem those doctors and members of the nursing profession who, in the exercise of their calling, endeavor to fulfill the demands of their Christian vocation before any merely human interest. Let them therefore continue constant in their resolution always to support those lines of action which accord with faith and with right reason. And let them strive to win agreement and support for these policies among their professional colleagues. Moreover, they should regard it as an essential part of their skill to make themselves fully proficient in this difficult field of medical knowledge. For then, when married couples ask for their advice, they may be in a position to give them right counsel and to point them in the proper direction. Married couples have a right to expect this much from them.
Source: Humanae Vitae (Vatican.va)