The effectiveness of the methods of Natural Family Planning works in two ways—for achieving and postponing pregnancy.
This is important news to married couples because typically "effectiveness" is thought to be only related to avoiding pregnancy.
In NFP education, both husband and wife learn about their combined fertility and are taught how to live in harmony with God's design. They are also encouraged to discern whether God is calling them to attempt to have a child or to postpone a pregnancy.
The methods of NFP are the only approach to true responsible parenthood because they respect God's design for married love!
Attempting a Pregnancy
NFP teaches a husband and wife to identify their "fertile window." This is the time in the wife's menstrual cycle when she is ovulating and therefore more likely to become pregnant if she and her husband have conjugal relations. The fertile window includes information about three biological facts:
- Female ovulation with it corresponding sign of cervical fluid (mucus)
- The life of the female mature egg (12 to 24 hours)
- The life of the male sperm in the female body when cervical fluid is present (up to 6 days)
When a husband and wife understand their combined fertility, they can plan their conjugal relations during the fertile time in order to attempt to become pregnant. This can help them achieve pregnancy quicker than with random acts of sexual intercourse. Typically, in about 85% of couples, random intercourse will result in pregnancy in about one year. NFP, on the other hand, can help a husband and wife become pregnant within 3-6 months.
| Percentage of Couples | NFP Method | Months to Achieve Pregnancy |
|---|---|---|
| 78% | Sympto-Thermal Method | 3 months1 |
| 81% | Sympto-Thermal Method | 6 months1 |
| 78% | Billings Ovulation Method | 4.7 months2 |
| 90% | Creighton Model, FertilityCareTM | 3 months3 |
| 98% | Creighton Model, FertilityCareTM | 6 months3 |
Notes
- C. Gnoth, D. Godehardt, E. Godehardt, P. Frank-Herrmann, G. Freundl, "Time to pregnancy: results of the German prospective study and impact on the management of infertility," Human Reproduction 18, no. 3 (2003): 1959.
- Research Team of the Ovulation Method Research and Reference Centre of Australia Ltd, "Study on the Billings Ovulation MethodTM and the achievement of pregnancy" (1999-2003), Web Statistics available from thebillingsovulationmethod.org/how-effective-is-the-billings-ovulation-method™/success-in-achieving-pregnancy.
- T. W. Hilgers, K. D. Daly, A. M. Prebil, S. K. Hilgers, "Cumulative pregnancy rates in patients with apparently normal fertility and fertility-focused intercourse," Journal of Reproductive Medicine 37, no. 10 (1992): 864-866.
Avoiding a Pregnancy
When wishing to postpone or avoid pregnancy, studies show that couples who follow their NFP method’s guidelines correctly, and all the time, achieve effectiveness rates of 97-99%.
Others, who are unclear about their family planning intention (i.e., spacing or limiting pregnancy) or are less motivated, will not consistently follow the method’s guidelines and have a lower effectiveness rate of 80-90%.
Notes
The above effectiveness rates are based upon research of the methods of NFP. The following is a sample of the studies
- R. Fehring, “Research in Natural Family Planning: A Review of Studies from 1998-2003,” in Current Medical Research, 14 (Summer/Fall 2003).
- P. Frank-Herrmann, 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 22 (2007): 1310-1319.
- M. Manhart, M. Duane, A. Lind, I. Sinai, J. Golden-Tevald, "Fertility awareness-based methods of family planning: A Review of effectiveness for avoiding pregnancy using SORT," Osteopathic Family Physician 5, no. 1 (2013): 1-8.
- For foundational NFP studies, see also Section II, “Effectiveness of NFP Method,” in Fehring and Kambic, Natural Family Planning Bibliography (1995): 9-12; available at Effectiveness of NFP Methods.