NFP
Natural Family Planning (NFP) is not contraception. NFP gives a married couple a way to space out childbirths and limit the total number of children.
NFP uses the natural increase and decrease in fertility built into a woman’s menstrual cycle to increase or decrease the possibility of conception. There are several different modern effective methods of NFP. Each identifies the most fertile time in a woman’s cycle and requires the couple to abstain from sexual intercourse during that time, if they wish to avoid conception.
The effectiveness of any method of NFP varies from one couple to another. The Sympto-Thermal Method (STM) of NFP is over 99% effective in postponing pregnancy.
(Source: Couple to Couple League)