Interesting. I've never thought of it this way.
When is a human being a human being then? Birth? A specific trimester of the pregnancy? I'm curious to hear you're stance on this because I've been on the fence about things like abortion for a long time and I think you might have something here that'll allow me to put the issue to rest.
I don't really think that anyone here is qualified to make a medical opinion of what a human being is, but if you want a philosophical opinion, then one could make the case for any trimester you want. Just a few facts to consider:
At 6 weeks the embryo is about 1/5 of an inch in length. A primitive heart is beating. Head, mouth, liver, and intestines begin to take shape.
At 10 weeks the embryo is now about 1 inch in length. Facial features, limbs, hands, feet, fingers, and toes become apparent. The nervous system is responsive and many of the internal organs begin to function.
At 14 weeks the fetus is now 3 inches long and weighs almost an ounce. The muscles begin to develop and sex organs form. Eyelids, fingernails, and toenails also form. The child’s spontaneous movements can be observed.
At 18 weeks the fetus is now about 5 inches long. The child blinks, grasps, and moves her mouth. Hair grows on the head and body.
At 22 weeks the fetus now weighs approximately 1/2 a pound and spans about 10 inches from head to toe. Sweat glands develop, and the external skin has turned from transparent to opaque.
At 26 weeks the fetus can now inhale, exhale and even cry. Eyes have completely formed, and the tongue has developed taste buds. Under intensive medical care the fetus has over a 50% chance of surviving outside the womb.
At 30 weeks the fetus is usually capable of living outside the womb and would be considered premature at birth.
At 40 weeks the child is now ready to live outside of his mother’s womb.
In my non-professional opinion, I can't really see how someone can say that a fetus is any different from any baby once it reaches the third trimester. The second trimester and even late into the first trimester seems to be extremely dangerous territory to me. The fetus has every appearance of a human child with the exception of size, and I'm not sure that can be a very reliable determining factor. I would not be comfortable with any abortion procedure after about 8 weeks.