I'm pro-choice, so you already know what I'm going to say
Even if you believe life begins at conception, I don't see how you could argue with termination of an extremely high-risk pregnancy in which it is highly probable that mother, baby, or both will die. Ectopic pregnancies, for example, are routinely terminated. You're talking about one life definitely ending, vs. two lives probably ending.
Interesting side note: If you have ever had an abortion, any subsequent pregnancy is automatically high-risk.