actually, I would say the life of the innocent human being is worth more than all four...especially when you consider the odds of a woman losing her foot because she delivers her baby at full term......
The problem is the odds where people make exceptions and one exception diminishes all human life. Would it be fair to say you believe a woman should be forced to carry a pregnancy unless it will result in the death of both?
If one truly values life an abortion can never be acceptable as a preventive measure regardless of how certain doctors may feel a woman's life is in danger.
For example, the almost certain conclusion major kidney damage or a massive stroke resulting from uncontrolled high blood pressure, due to the defective body of a woman, can not justify the killing of an innocent, healthy human being.
As a society are we prepared to hospitalize the woman, possibly against her will, so as to ensure if major damage does occur life supporting procedures can be implemented until the birth occurs and then let her expire or live out the rest of her life institutionalized?
If we know there is a distinct possibility a woman may die due to her medical condition do we not have the obligation, the moral right, to hospitalize her to ensure the fetus (a human being) survives? Is not entrusting the life of a fetus to a woman whose medical condition greatly enhances her chances of dying, resulting in the death of the fetus, tantamount to gross negligence?
Should a zygote/embryo/fetus be considered a human being does not society have the same responsibility towards it as society does towards a new born?
There are laws which prevent woman from taking drugs while pregnant as it may harm the fetus. Where do we stand regarding the incorrect food a woman may consume when afflicted with a certain illness? For example: high blood pressure and fatty or salty foods?
While a new-born's mother may die the new-born will continue living for a period of time enabling someone to rescue it. In the case of a zygote/embryo/fetus the rescue time is considerably shorter. Does the consumption of a McDonald's burger constitute child endangerment?
The bottom line, as they say, is are we prepared to protect the zygotes, embryos and fetuses to the same degree we protect other groups of human beings?
Should a pregnant woman be allowed to go skiing? We definitely wouldn't allow someone to strap a baby on their back and head down a ski hill. Should a pregnant woman be allowed to do any activity which might contain an element of danger?
Classifying a zygote/embryo/fetus as a human being would result in a lot more than outlawing abortion. It would affect every aspect of a woman's life and if it didn't it would make a mockery out of the sanctity of life and what it means to be a human being.
NB. I noticed you answered the question regarding taking the chance medical problems may arise, however, I do have skepticism should a member of your family be faced with such a situation.