no. 1119 for the year 2005 which includes the following:

A married woman with four children suffers from a debilitating illness. Physicians advised her against having more children and using any temporary means of contraception, such as birth control pills, because they will harm her her. She has no other alternative except to undergo tubal ligation which will permanently terminate the potential to reproduce. She is inquiring about the position of Islamic law on this issue.

Permanent sterilization by interrupting the functions of the body is prohibited since it damages what Allah entrusted to us. Moreover, it undermines one of the five objectives which Islamic law seeks to preserve: religion, life, intellect, progeny and wealth.

The ruling 
It is forbidden to terminate the ability to procreate -through tubal ligation or other means- except for a justifiable necessity such as when there is fear that a future pregnancy could threaten a woman's life, damage or destroy one of her organs, or when it is feared that a terminal illness could spread to the fetus, in which case this falls under the legal axiom which states: "Necessity renders prohibited things permissible".

Allah Almighty knows best.