I am Catholic, and this is a very tough issue for me. There seems to be a loophole that goes something like this:
1. Human life begins at contraception
2. According to the Church, an embryo onwards is a human life and deserves protection from the law. Conversely, the fetus is therefore responsible under the law.
3. Defending your life by taking another is justifiable.
4. If an embryo or fetus causes the mother grave injury, the mother has a moral pass and can defend herself with an abortion.
I think the way the Church gets around this is through the antepartem diagnosis clause.
It is also important to note that ectopic pregnancy is not an "abortion" issue. Removal of the part of the tube that contains the baby is not, as far as medical procedures go, an abortion.
Morally, the difference between abortion and the loss of a child implanted ectopically is that, when the doctor removes the part of the fallopian tube that contains the baby, he does not directly harm him or her. The child, sadly, dies in this process, but the death is not intentional. In an abortion, a baby is directly, bodily attacked.
"1. Human life begins at contraception "
Is this a really good Freudian slip, or merely a typo? ;-D