A Woman's Obligation to Undergo a Cesarean Section in Order to Save her Life-threatened Fetus
Background
A woman at the end of her pregnancy is carrying a Down's syndrome child. At birth the child enters a life-threatening situation. The only way to save the child is to perform an emergency cesarean. The mother has previously stated that the child is unwanted.

Question
Is she obligated to undergo the cesarean or may she refuse hence resulting in the child's death in a passive fashion?

Answers
Since a cesarean is not defined as halachic risk, the woman is obligated by the Torah to undergo the cesarean in order to save the child. Further (according to Rabbi Y. Weiner), if a situation arises in which an invasive inter-utero procedure must be performed in order to correct some life-threatening anomaly of the child, the mother must also agree to this.
If the mother is carrying a child who is defined as a treifah (the child even with medcial intervention will not survive a full year) then the mother has the right to refuse the cesarean even if it results in the child's death.