Well that’s the case isn’t it. You rate not abandoning normal sexual relations (I’m assuming procreation here) above risking the death of a fetus or multiple fetuses.
The reality is you have total control over whether a fetus dies by abstaining from sex or using birth control unless a gun is being held to your head to procreate.
Finally, you call it a corner case but the truth is it’s just the way pregnancy works. If you want to call a fetus a child and life starting at conception then you choose to play Russian roulette (using the equivalent of 1-5 bullets) with your “child’s” life.
If I believed as you’d do I would find procreation immoral.
However since I don’t and I understand that until there is something like a functioning brain it’s not a person yet. By the time there is after 20+ weeks the risk of miscarriage way down in the single digits.
I’m also not against third trimester abortions for fetal defects. It’s the parents responsibility to determine what to do about the imminent fate of their child and I don’t think the government or anyone else should be forcing a one size fits all policy on the traumatic end to a wanted pregnancy.