Studies that examined the effectiveness of NFP  in avoiding pregnancy

Many of the effectiveness studies of the symptothermal double-check method (STM) of natural family planning have been done in Europe, the data being collated in Germany by groups in Dusseldorf and Heidelberg. These studies have shown that :

  • (a) the symptothermal double-check method when used correctly is an effective method of family planning.
  • (b) The symptothermal double-check method is acceptable and has a low drop-out rate.

The low drop-out rate because of dissatisfaction or difficulties with Natural Family Planning, and the low pregnancy rate also negate the other long-held belief that abstinence is a major obstacle to Natural Family Planning.3

  • The Heidelberg 2007 study by Frank-Hermann et al2 confirms that the “symptothermal double-check method” of natural family planning that uses two indicators of fertility, – basal body temperature and cervical mucus observations to determine the end of the fertile time, and cervical mucus plus a calculation to identify the beginning of the fertile time, – is an effective and acceptable method of family planning”. In their study2 after 13 cycles the unintended pregnancy rate for perfect use, (i.e. true method effectiveness) was 0.43 per 100 women (see table vii, and page 9 of this study 2), and the over-all rate of unintended pregnancy was 1.8 per 100 women, (Kaplan-Meier method of assessment used).
  • The 1989 -1995 European Multicenter study by Prof G. Freundl et al3, University of Dusseldorf, shows the effectiveness of the ‘symptothermal double-check method’ of natural family planning measured by the Kaplan-Meier method. In this study of 1046 women who contributed 16,865 cycles of exposure, 34 unintended pregnancies occurred. This gives an unintended pregnancy rate of 2.6% at the end of the first 12 cycles of use, and compares favourably with current contraceptive methods, such as IUDs.3 Most pregnancies occurred because of deliberate intercourse in the fertile phase (‘user failure’). This study by Freundl found that “users of the ‘double-check’ methods have the lowest rate of unintended pregnancies. This is the most important result since women want to use the most effective natural method”.3

The ‘symptothermal double-check method’ uses two fertility indicators to define the beginning of the fertile phase, (cervical mucus observation and some kind of calculation rule), and two fertility indicators to define the end of the fertile phase, (basal body temperature and mucus observation).

The ‘symptothermal single-check method’ uses one indicator (cervical mucus observation) to mark the beginning of the fertile phase and one indicator (basal body temperature) to mark the end of the fertile phase.3

  1. Freundl G.; Prospective European multi-center study of natural family planning (1989-1992): interim results; Adv. in contraception; 1993, 9; 269-283.
  2. P.Frank-Hermann et al; ‘The effectiveness of a fertility awareness based method to avoid pregnancy in relation to a couple’s sexual behaviour during the fertile time: a prospective longitudinal study; Human Reproduction, pages 5,7; Feb 2007; p1-10. (on internet)
  3. Freundl G; ‘European multicenter study of natural family planning (1989-1995): efficacy and drop-out’; Advances in contraception; 1999;15; 69-83. This article gives a review of other studies on pages 79,80.

To be most effective, the woman must be taught the Symptothermal Double-Check Method of Natural Family Planning by a qualified natural family planning teacher.