My husband and I use Creighton U. method of NFP.  I have messed up cycles so there is a little more abstinence for us than for other people I know who use it.  It is effective if you learn the method and use it (abstain when peak fertility).  My sister has used it for 9 years successfully.  I have thought about taking a Couple to Couple League Sympto-Thermal class only because Creighton relies totally on Cervical mucus observation and temp would be a good double check. ...