It is important to understand exactly what an abortion is before answering this question. Abortion means that something has happened which caused the fetus to be expelled from the womb, with death of the fetus occurring shortly thereafter. When a woman has a miscarriage, that is an abortion. When a woman already has or develops some medical conditions while pregnant, they may develop into a situation threatening the life of the woman.
While many doctors today do not actually swear to practice medicine in accordance with the Hippocratic Oath in particular, most do agree to some form of a pledge to conduct themselves and their medical practice with the best interest of their patients as the most important consideration. Doctors need to evaluate the circumstances and medical risks of every pregnancy individually; they also need to decide their personal beliefs and priorities in response to such situations.
Some doctors may identify types of situations in which they feel ending the pregnancy is in the best interest of the woman and that they are abiding by their commitment to practice medicine in a moral and ethical manner by doing so.
I think that in some cases, you need an abortion.