Is having your tubes tied for a medical reason allowed?

[StratusRose]

Please, please, learn a real method of NFP. NFP IS effective when used properly, 90-95%. If you use only the post ovulatory days, the effectiveness is even higher.
%between%

Notice that the effectiveness goes up based on the motivation of each couple to avoid pregnancy:

I don’t know about the Billings Method, but I do know that CCL’s STM method boasts 99% effectiveness when used correctly.