By “works” I assume you mean low failure rates?
To anyone here who is very knowledgable about NFP, what do you say about the following?
The reported failure rates for modern NFP methods range from less than 1 to 5 percent for perfect use, and 2 to 25 percent for typical use.16,19–30 The few randomized controlled trials of NFP methods have been limited by poor recruitment and high dropout rates.31 Therefore, the evidence for NFP methods is based on observational trials that are prone to selection bias.
I think after that was written, another randomised clinical trial’s results may have come out. EHFM I think stands for “electronic hormonal fertility monitor” and CMM for “cervical mucus monitoring”
The net correct use efficacy of both the EHFM and CMM group is very good, i.e., 98- 100% survival rate (or a 0 – 2 pregnancy rate per 100 women over 12 months of use) and compares with what is found in the literature (Trussell 2004; Trussell 2010). As hypothesized, the monitor group has better total pregnancy rates than the mucus group, i.e., a 7% unintended pregnancy rate among the monitor group versus 18% among the mucus group. The differences in pregnancy rates between the monitor and mucus group are similar to the differences that were found in a previous cohort comparison study of the monitor plus mucus versus mucus alone as two methods of NFP (Fehring, et al, 2009). The low unintended pregnancy rate (both perfect and total) are comparable to the pregnancy rates that were determined in a large European study that used mucus plus basal body temperature as a double check for the beginning and end of the fertile phase of the menstrual cycle (Frank-Herrmann et al. 2007) and with a pilot cohort study of the online FABM conducted by the authors of this study, i.e., a 9% pregnancy rate among ovulating, non-breastfeeding participants (Fehring, et al., 2011).
Here is a review of this study: usccb.org/issues-and-action/marriage-and-family/natural-family-planning/medical-research/upload/CMR-Winter-Spring-2013-FINAL.pdf
A study by the World Health Organization involving 869 fertile women from Australia, India, Ireland, the Philippines, and El Salvador found that 93% could accurately interpret their body’s signals regardless of education and culture.2] In a 36-month study of 5,752 women, the method was 99.86% effective.47]
The Standard Days method was developed and proven by the researchers at the Institute for Reproductive Health of Georgetown University. CycleBeads, unaffiliated with religious teachings, is a visual tool based on the Standard Days method. According to the Institute of Reproductive Health, when used as birth control, CB has a 95% effectiveness rating. Computer programs are available to help track fertility on a calendar.48]
This may be the study that is discussed here from 2002:
Natural Family Planning Method As Effective As Contraceptive Pill, New Research Finds
This came out in 1998:
DALLAS—The Creighton method of natural family planning (NFP) is roughly as effective as the birth control pill when used to avoid pregnancy, according to a 14-year, five-state study published this summer in a U.S. medical journal.
The study, which appeared in the June issue of the Journal of Reproductive Medicine, distributed to obstetrician-gynecologists, showed the method to have a 99.5% rate for method effectiveness, that is, when it is taught and used precisely, and a 96.8% use effectiveness rate, a “real-life” rate that includes teaching or use errors.
Read more: ncregister.com/site/article/study_confirms_creighton_methods_reliability_in_nfp/#ixzz3wKeENhQR