.. Yeah, that only works if you have a regular cycle. Many women don’t, and I never did, which led to a hysterectomy. A transplant recipient should avoid the number of blood transfusions that I needed. Sometimes I went a year with no cycle occurring, then had one continue for 14 months.
Personally, I think there should be some form of backup if you’re not looking to have children at the time you’re intimate. The Human body is affected by many things, and cycle-charting isn’t always completely accurate.
Also, the male half determines the baby’s sex.
The catholic method is the only one pleasing to G-d
All birth control that involves medical intervention or prophylactics is evil
You have to be a VERY IN CONTROL MALE however. If you don’t want a CATHOLIC SIZED FAMILY !