There are circumstances when giving birth will take the life of the mother and may also produce a dead baby. Granted those cases are rare but they happen. If that possibility exists, who has the responsibility and right to make the decision? Is it you, or the state, or anyone not directly involved with that decision and not subject to the direct consequences of that decision? I don't believe so.
Do we have the right and responsibility to try to influence those who would choose an abortion which is not absolutely necessary? Of course. ...wars can either be just or unjust; and it is perfectly moral to support a just war.
Who and what determines a "just war"? That is usually the winner. North Vietnam won their war against South Vietnam and the U.S. so from their perspective it was a just war. That war produced a larger and stronger communist country. Was that a moral outcome? Many of the soldiers who fought and died in Vietnam were drafted; it was not their choice to go thousands of miles from their home and engage in war - could they not be called innocent also? However you look at that, there were thousands of innocent civilians killed. Of course war and abortion are different but there are similarities and it is very important who chooses either of those activities and why.
In this day and age, life threatening pregnancies are so rare that they are hardly an issue. However, it is not morally permissible for a woman to deliberately take the life of her unborn child even if pregnancy or childbirth poses a threat to her life or health. However, it is permissible to treat the underlying condition or illness even if such treatment poses a risk to the life of the fetus. But as you yourself have admitted, these cases are pretty rare and even if one admits that abortion is permissible in those cases—which I do not—this kind of situation certainly does not justify the 96% of abortions that are performed for reasons of convenience, birth control, etc.
There are similarities between war and abortion in that both involve the destruction of innocent human life but in abortion only innocent lives are lost.
Here are the criteria which the Catechism of the Catholic Church sets out for a just war:
“—the damage inflicted by the aggressor on the nation or the community of nations must be lasting, grave, and certain;
—all other means of putting an end to it must have been shown to be impractical or ineffective;
—there must be serious prospect of success;
—the use of arms must not produce evils and disorders graver than the evil to be eliminated. The power of modern means of destruction weighs very heavily in evaluating this condition.
These are the traditional elements enumerated in what is called the ‘just war’ doctrine.
The evaluation of these conditions for moral legitimacy belongs to the prudential judgment of those who have responsibility for the common good.”
(n. 2309)