These occurrences are written down in a monthly menstrual chart which allows the couple to pinpoint, with great accuracy, the days of highest fertility. If pregnancy is not desired that month, the couple will abstain until the woman's 'signs' indicate that her fertility is over for that menstrual cycle. There are several methods of NFP that couples use. There is the Billings Method, the Creighton Model, and the Sympto-thermal Method, to name a few. Each method is basically the same, with slight variations.
Some couples find they prefer one method over another.
There is some debate in NFP circles as to which method is the most effective. Each couple will ultimately determine which method is best for them. It is true that many couples who use NFP do have large families. This could be for several reasons. First, and most importantly, many generous couples desire large families.