A Fetal Life in a Dead Mother

A woman who is legally dead, is being kept on "life support" in a Texas hospital against the wishes of her husband and parents.  She is being maintained on "life support" solely to sustain the viability of her 21-week old fetus.  Physicians have refused to honor the wishes of the family, arguing that Texas law prevents them from withholding "life-sustaining treatment" from a pregnant patient.  The family contends, however, that since the mother has been declared "brain-dead" she can no longer be considered a pregnant patient, since a "patient," by definition, is someone who is alive.  Physicians intend to continue the present regimen until the fetus has reached the age when a caesarian section can be performed.

This fetus is now approaching extra-uterine viability - a fact which makes this case difficult to morally adjudicate.  However, if the fetus were as little as 4 weeks of gestational age, or if the fetus were as much as 30 weeks gestational age, how one would feel about this tragic set of events might be quite different.

If the fetus is to be the sole consideration here, then perhaps a caesarian section should not even be considered, there being no question that a fetus has a far better chance of survival in-utero than ex-utero.  Assuming no complicating medical factors, would it be ethical to continue to maintain this "natural" form of fetal nurturing rather than proceeding with a C-section?  Would it be ethical at 4 weeks gestation?  Would it be ethical at 30 weeks gestation?