When I said stress was the trigger for abortion it included genetic problems. They stress either the physical well being of the female or the direct development of the fetus in animals or humans. The point was to show that abortion is a natural reaction to stress, not to devalue the fetus. Nobody devalues a fetus, even animals can show what looks like grief over a dead fetus. Abortion, spontaneous or induced, is not a happy occasion.
If abortion is spontaneous and natural in animals it seems that it makes sense not to simply dismiss it in humans without asking why humans choose to abort. After all we are animals so the question is why do women abort a fetus. These are the reasons
Not ready for a child or another child ………….. 25%
Cannot financially support a child ……………… 23%
Have other people depending on me.. .………….19%
Unstable relationship with father or other………….8%
Not mature enough………………….………….......……..7%
Job and education leave no time for a child……….4%
Health of mother…………………………….........…………4%
Health of fetus…………………………………..........………3%
Incest, rape, family and father want abortion……….2%
Other…………………………………………...............…………6%
Reasons U.S. Women Have Abortions: Quantitative and Qualitative Perspectives | Guttmacher Institute
Every reason , with the exception of "other," represents a stress either to the family, to the female or to the potential child. The list has no frivolous reasons. If, after thinking and reasoning a woman says that the stress of adding a child or another child to situation already unsuited to raising a child will be bad for the family, the child and the woman herself it makes sense to listen to what she is saying. Why would one ignore someone that says, "I can't do this" when this means the future of a child. Every child needs a home where there is a physical, mental and emotional capacity to care, love, and nurture the well being of all the family. Very few children grow up well to become responsible members of society without a family that can provide those essentials to healthy lives.
Extreme stress in nature automatically causes spontaneous abortion in animals. With the capacity to think and reason humans have an obligation to consider the future of the family, the child and the woman, an obligation to think very carefully about the survival a child to a situation that lacks support for that child. There are a few children that survive horrendous situations and go on to become contributing adults, but they are so few that denying abortions to thinking reasoning women is not a wise policy.
The mechanism that assures the survival of the herd is exactly the same as the mechanism that assures the health of human society. The only difference is that humans have to think about it and animals don't.