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. 2025 Jul 8;92(3):336–349. doi: 10.1177/00243639251347842

The State of the Science of Natural Family Planning: A Report from NFP Scientists’ Meeting Held in Orlando, FL, September 4, 2024

Michael D Manhart 1,✉, Richard J Fehring 2
PMCID: PMC12237956  PMID: 40641837

Abstract

A one-day meeting was held as a pre-conference to the Catholic Medical Association Annual Educational event in 2024. A panel of eighteen physicians, scientists, and researchers involved in NFP work was convened to review the available evidence in four topical areas: (i) evidence for effectiveness of NFP methods to postpone and achieve pregnancy, (ii) evidence for effectiveness in the postpartum and perimenopause transition periods, (iii) evaluate the current state of technology in NFP (specifically app and quantitative hormone monitoring), and (iv) evidence examining the impact of NFP on marital relations. In each topical area, the panel worked to reach a consensus opinion on the currently available evidence and identified priorities for further research. Results from these discussions and a set of priorities for further work are presented here.

Summary: An expert panel was convened to review the current evidence supporting use of NFP in various settings, utilization of new technology, and the impact of NFP on marital dynamics. Results from these discussions and a set of priorities for further work are presented here.

Keywords: Breastfeeding, Divorce, Fertility awareness, Fertility awareness information technology, Fertility health, Infertility, Menstrual cycle, NFP, Perimenopause, Postpartum

Introduction

In 2018, a one-day meeting of physicians, professional nurses, and scientists actively involved in Natural Family Planning (NFP) research was held to review the state of the science of NFP and consider future priorities (Manhart and Fehring 2018). At that time, the assembled group felt it would be valuable to hold a similar meeting in about five years and to include younger scientists.

Responding to this, a one-day meeting was held as a pre-conference to the Catholic Medical Association Annual Educational event in 2024. Based on the call in the encyclical Humane Vitae for scientists to develop secure methods of natural family planning and to study the benefits and challenges that they provide for married couples, the meeting objectives were:

  • Determine the gaps in research evidence for effective evidenced-based methods of natural family planning (NFP) for women with all reproductive categories.

  • Determine the gaps in the research and development of new technology for providing NFP services.

  • Determine the gaps in the research literature that determine the benefits and challenges with use of NFP among married couples.

  • Provide prioritized ideas for future research or needs for research from the analysis of evidence gaps from objectives 1–3.

A panel of eighteen physicians, scientists, and researchers involved in NFP work was convened to review the available evidence in four topical areas and, to the extent possible, reach a consensus opinion on the currently available evidence and call out priorities for further research. The meeting was open to CMA attendees and an audience of approximately 100 added to the dialogue. Ideas for future research priorities were captured throughout the day, organized by topical area and then distributed to the panelists for individual voting. The fifteen priorities that received the most votes from the panelists in total are presented.

We report here a summary of the meeting along with a set of priorities for future work in specific areas.

Evidence for Effectiveness of NFP Methods to Postpone and Achieve Pregnancy

Use to Avoid

Two systematic reviews examining the quality of evidence when NFP is used to avoid/postpone pregnancy have been published in the last ten years (Manhart et al. 2013; Peragallo Urrutia et al. 2018). Although both reviews evaluated studies using a common set of research design and execution criteria, each employed different grading scales to determine individual study quality; Manhart et al. employed SORT criteria (Ebell et al. 2004) while Urrutia et al. utilized the USPHS scales. Studies of the Billings (Bhargava et al. 1996), Sympto Thermal Method (STM) (Frank Herrmann 2007), Marquette mucus-only, Marquette hormone-only (Fehring 2013), Standard Days (Arévalo, Jennings and Sinai 2002), and Two Day (Arévalo et al. 2004) methods ranked among the top-quality scores in both reviews. Perfect use unintended pregnancy rates (pregnancies only in perfect use cycles) ranged from 0 to 5 per 100-women years. Typical use unintended pregnancy rates (unintended pregnancies in all cycles) ranged from <2 to 14 per 100-woman years.

Comparative studies would help define if significant differences in effectiveness between methods exist, but today such studies are rare. A retrospective cohort study compared 315 Creighton-trained users to 313 Marquette model-trained users and found no difference in correct use unintended pregnancy rates, but the Marquette method had significantly fewer total unintended pregnancies at 12 months (12% vs 23% respectively, p < 0.05) (Fehring et al. 2009). Fehring et al. (2013) demonstrated significant differences in unintended pregnancy rates in their randomized comparative trail of Electronic Fertility Hormone Monitor (EFHM) (7% typical use) versus cervical mucus (18.5% typical use). Similarly, Fehring and Schneider (2017) in a two-year study found those using the EFHM alone had a typical unintended pregnancy rate of 6% and 19% for women using mucus only to avoid. Notably, those women using both EFHM and mucus to avoid had a typical unintended pregnancy rate of 18%.

Since the systematic reviews were published, a few additional effectiveness studies have been published. Jennings et al. (2019) reported unintended pregnancy rates of 1% for perfect use and 5% for typical use among those using the DOT app (DOT = Dynamic Optimal Timing) to avoid pregnancy. Use of barriers during the app-defined fertile days was considered correct use; frequency of condom use was not reported in this study. The DOT app requires the user to only enter the start of the menstrual cycle; the fertile window is calculated based on day-specific probabilities of conception. While this represents a very simple method, women who experience cycles outside of 20–40 days length and/or a cycle variation of less than 10 days will be told by the app they are ineligible to use the algorithm. Ineligibility due to cycle variation resulted in discontinuation from the study of 1 in every 7 women and was the most frequent reason for study exit.

Pearson et al. (2021) reported on a United States cohort of Natural Cycle app users seeking to avoid pregnancy (n = 5,879) and found a typical unintended pregnancy rate of 7.2%, consistent with previously reported results. In this cohort, most users employed either a condom (53%) or withdrawal (25%) during the app-identified fertile days while only 11% abstained during the fertile window.

Mu, Fehring and Bouchard (2022) examined over 1,200 women from ten Marquette Model training centers who were seeking to avoid pregnancy. Most (61%) were postpartum and breastfeeding, one-third (33%) were regular cycling and 6% were classified as irregular cycling (had cycles outside 21–35 days in length). The total typical unintended pregnancy rate was 6.7%: 2.8% in the regular cycling subset, 8.0% in postpartum women, and 4.3% in the irregular cycling group. As in earlier studies, women using the EFHM had lower pregnancy rates compared with those using cervical mucus alone and with those using both EFHM and mucus.

The panel felt that at least one of the available methods works well for most people and most methods are good at determining post-ovulatory infertility, but improvements could be made in better defining prospectively the beginning of the fertile window. Given the large variations in an individual's acceptable level of complexity, instruction, cost, ability to fit within their patterns of daily life, and tolerance for unintended pregnancy (which modulate over time) the panel felt that no one method is preferred.

The effectiveness of NFP methods in daily use can be influenced by several factors. These include the quality of instruction and complexity of teaching while learning a specific method, the accuracy of the indicators of fertility employed by a particular method, the motivation to avoid or achieve by both partners, and the level of partner support for using NFP. Further work to understand these and other influences on effectiveness is needed.

An identified limitation of the current evidence is that most effectiveness studies have included generally healthy regularly cycling women. Formal investigations of various methods of NFP in different cohorts of women (non-normal cycling, identified conditions like PCOS, women of various ages, etc.) is warranted. There is also a need for comparison of methods or indicators of fertility in high-quality studies and, ideally, in random comparisons. Beyond this, NFP methods need more generalizable evidence for effectiveness when used in the “real world.”

Use to Achieve

Duane et al. (2022) reviewed the limited available data exploring the use of NFP to achieve pregnancy. There are only a few studies (or subsets of larger studies) that have explored this question, and most are cohort studies, so comparison of NFP effectiveness relative to just having frequent intercourse is unknown.

The known biology of fertility and the current data suggest knowledge of the optimal days to conceive does shorten time to pregnancy, but formal comparisons have not been conducted as of now. Bouchard et al. (2018) demonstrated the utility of focused fertility-timing intercourse within the fertile window. Women using the EFHM to define the fertile window had pregnancy rates of 80% and 83% after 6 and 12 cycles use, respectively; those using cervical mucus monitoring had rates of 48% and 73% after 6 and 12 cycles respectively, while women using both EFHM and mucus had pregnancy rates intermediate to either alone. Favaro et al. (2021) analyzed time to pregnancy among women 18–45 years of age using Natural Cycles app to define the fertile window. Here in over 5,300 women the overall 6 and 12 cycle pregnancy rates were 61% and 74% with median time to pregnancy of 4 cycles. In a subset of 613 women under 35 years old with <5 days variation in cycle length and diligently recording intercourse in the app, pregnancy rates were 88% and 95% respectively with a median time to pregnancy of 2 cycles.

Whether focused fertility is better than random intercourse has not been diligently investigated to this point. A randomized study comparing mucus-based NFP instruction with frequent intercourse showed no difference in pregnancy rates but was under powered (Stanford, Smith and Varner 2014). Johnson et al. (2020) did find a higher pregnancy rate after two cycles (36%) in persons seeking pregnancy and using daily urinary hormone monitoring compared with non-using controls (28%). Wise et al. (2023) examined fecundability in a large cohort of women seeking pregnancy (n = 5,551) randomized to a fertility tracking or not and found by 12 cycles 64% and 63% had conceived in the two groups, respectively. The results are confounded by the fact that 69% of both groups were already using a fertility tracker at study entry.

In persons with known subfertility, there is documented benefit from identifying one or more of the underlying causes and addressing these (summarized in Duane et al. 2022). Current support for these restorative approaches lies in cohort studies (see Duane et al. 2022 table 5); success rates in these studies are similar to those reported in IVF studies. These restorative approaches have shown benefit among couples who have failed to achieve even after several rounds of ART/IVF (Boyle et al. 2018; Boyle, Stanford and Zecevic 2022).

Lacking today is comparison to standard medical and surgical treatments of endometriosis, PCOS, metabolic syndrome, thyroid problems, lifestyle problems, male infertility, etc. to establish if there are important differences in outcomes. Setting aside the ethical and moral issues of IVF, today there is no high-quality evidence that the restorative systems are better than IVF.

What may be demonstrated in comparative studies is that charting and monitoring the menstrual cycles during various treatments could add to the diagnosis of underlying condition(s) and/or improve monitoring individual responses to treatments.

The panel identified these priorities for future work:

  • High-quality cohort and comparative effectiveness studies of various methods of NFP (to avoid) in different cohorts of women (non-normal cycling, identified conditions like PCOS, endometriosis, women of various ages, etc.).

  • Well-designed studies to demonstrate time to pregnancy is faster with user knowledge of the fertile window compared with frequent intercourse/no knowledge.

Evidence for Effectiveness in Transition Periods

Postpartum

In the US, over 3 million women give birth each year; 86% attempt to breastfeed, 58% are breastfeeding at 6 months and 37% at 12 months. Sixty percent indicate they breastfed for a shorter duration than desired (Setty-Venugopal and Upadhyay 2002). The proportion of women using NFP during this transition is unkonwn, but the desire to remain drug-free, and/or a desire for more children in the future suggests it is a time when NFP may be an attractive form of family planning to many.

Lactational amenorrhea, when practiced according to the guidelines, has a 2% probability of unintended pregnancy in the first 6 months after birth (Kennedy and Visness (1992). A Cochrane review of LAM studies (Van der Wijden and Manion 2015) showed little or no difference in pregnancy rates compared with exclusive breastfeeding.

Poorly understood today are the influences of frequency of suckling, use of pacifiers, mother/baby separation due to work, and pumping on LAM/exclusive breastfeeding effectiveness. In addition, we do not know the pregnancy rate in mothers doing nothing during the postpartum transition prior to the first menstruation to have a “baseline rate” for comparison. Finally, predicting which women will experience an earlier (or later) than expected return of fertility when complying with LAM guidelines is undefined today.

A systematic review (Redmond et al. 2022) of NFP in postpartum mothers revealed only four published studies; two were rated moderate- and two low-quality. The current evidence on the effectiveness of each fertility awareness-based method for postpartum women is very limited and of mostly low quality. More recently Schneider, Fehring and Bouchard (2023) reported on a retrospective analysis of 216 women using an updated postpartum protocol for the Marquette method. Unintended pregnancy rates at 12 months were 3.5% for typical use and 1.5% for correct use. Unintended pregnancy rates at 12 cycles were 2.7% for typical and 1.3% for correct use. More high-quality studies on the effectiveness of fertility awareness-based methods in postpartum women are needed.

The panel advised that future studies should include the following design elements: adjusting for/accounting for reduced fecundity in postpartum populations, effectiveness per cycle and per time are both needed for full understanding, and reporting of discontinuation reasons and rates. In addition, studies should include clear descriptions of populations included (e.g., amenorrheic versus cylcling, number of cycles postpartum) and more complete breastfeeding description (timing, exclusivity, mode of delivery).

The return of fertility postpartum is influenced by several factors which can complicate the use of NFP to avoid pregnancy. Menstrual bleeding, cervical mucus changes, LH changes, and urinary estrogen metabolites precede return to fertility and can demand long periods of abstinence to avoid pregnancy. Quantitative hormone monitoring may improve this, but testing needs to first document a benefit. Machine learning and AI techniques represent an unexplored area that may improve predictability. Beyond these factors, infant sleeping and eating patterns, the mother's prior breastfeeding history, illness, and stress are all important contributing factors (Redmond et al. 2022).

A small study (Bouchard et al. 2018) monitoring breastfeeding women using hormone assays revealed three distinct patterns: i) ovarian quiescence with delayed ovulation, ii) follicular activity with delayed ovulation, iii) early ovulation with short luteal phase. The mean time to first menses was 7.4 months and first ovulation was 8.4 months. Twenty-six percent (7/26) of the women in this cohort ovulated prior to menstruation; these women are most likely to experience an unintended pregnancy in the postpartum transition.

The panel identified these priorities for future work:

  • More high-quality studies on the effectiveness of fertility awareness-based methods in postpartum women are needed: Additional effectiveness studies for Marquette and Billings; other methods including quantitative hormone monitor and symptom-thermal methods need high quality studies.

  • Research regarding NFP use after pregnancy loss is needed.

Perimenopause

Fecundity (the physical capability to reproduce) decreases at 32 years of age and more rapidly by 37 years due to decrease in egg quality, aneuploidy, chromosome aberrations and maternal disease states (ACOG Opinion 589 2014). Live birth rates are very low after age 45; Laufer et al. (2004) reported a birth rate of 0.2% among more than 100,000 women over 45 years old. While live birth rates decline, spontaneous abortion rates dramatically increase. Nybo Andersen (2000) reported in a Danish population a spontaneous abortion rate of 8.9% in 20–24-year-old women and 74% in women over 45 years of age. In addition, still birth and ectopic pregnancy rates were also higher in older women. For women using NFP in the perimenopause transition, the concern over conception and early fetal loss is often as concerning as an unexpected live birth.

The STRAW model (Harlow et al. 2012) provides a framework to stage the transition from fertility to menopause, but it predominately relies on overall cycle length variations to determine early versus late perimenopause. Emerging data from NFP studies employing hormones (particularly FSH) and other markers may provide valuable insights to better define the STRAW stages.

A case series followed 42 women between 40–50 years old tracking their cycles using quantitative hormone monitoring and other observations (Meyers, Fehring and Schneider 2023). One of the 42 women conceived, but no live births occurred. The reserachers observed women in their early 40's had cycles with potentially important differences compared to younger healthy cycling women. These women displayed shorter regular cycles with earlier LH surges, long cycles (> 35 days) with delayed peaks, cycles with more than one LH surge (often close together), cycles showing no evidence of thermal shift, truncated E3G rises toward LH peak (<5 days), cycles with continuous elevated E3G and elevated LH levels, cycles with low E3G and low LH levels, and cycles with low E3G and elevated LH levels. In general, LH peak and progesterone levels may be lower than what we see in regular cycling women.

With respect to recent effectiveness studies of NFP in this transition period, a single prospective cohort study (Fehring and Mu 2014) of 160 perimenopausal women using the Marquette method was identified. There were 5 unintended pregnancies observed. Unfortunately, the population was relatively young (mean age 41.2 yrs) and only 15 participants were over 45 yrs.

The panel identified these priorities for future work:

  • Studies comparing the varied urinary hormonal scenarios during perimenopause with transvaginal ultrasound to confirm ovulation versus anovulation. What may seem to be ovulatory (e.g., rising E3G, LH surge, elevated progesterone following) in perimenopause may not be truly ovulatory because of overall lower hormone levels.

  • Identifying a better definition of the beginning and end of the fertile window and how this may shift as menopause approaches.

  • Based on the above, formulating an algorithm to know when to abstain or when there is no longer a need to monitor fertility (i.e., when actual fertility is too low to conceive even with signs of ovulation).

Technology and NFP

Apps and Systems for Charting Fertility Cycles

Cycle tracking apps are extremely popular. A survey of United Kingdom women 18 years and older found 34% of respondents had used a fertility tracking app with two-thirds of those aged 18–34 using tracking apps (Information Commission Office 2023). The popularity of fertility tracking apps continues to outpace the development of evidence supporting their use and limitations. Hence, anecdotal experience, social media, and popular opinion are more likely to drive use and attitudes of tracking than evidence-based data at least in the near term.

With the wide variety of apps and their features and functions, understanding how to categorize them to more effectively understand them is needed. Moglia et al. (2016) reviewed several popular free apps using the APPLICATIONS scoring system. For NFP users, the APPLICATIONS scoring system tends to overestimate app features (e.g., password protection, navigation ease, advertisements, connectivity, etc.) while underemphasizing the quality of clinical evidence supporting effectiveness. One approach to categorizing cycle trackers is to group them into one of three categories: menstrual tracking apps, NFP-specific apps, and hormone-tracking system apps.

Menstrual Tracking Apps. These are by far the largest category and are notable for their reliance on calendar tracking or undisclosed algorithms for any predictive outputs. The accuracy of these apps is uncertain. Worsfold et al. (2021) tested the top 10 apps based on downloads in the Apple store using five hypothetical women with differing cycle patterns that represent 90% of the biological variance observed. The apps accurately predicted the start of the next cycle for the woman that had consistent 28-day cycles, but as variance in length grew, predictability declined; incorrectly predicting the next cycle start date up to 8 days. Prediction of the day of ovulation was correct in just 8% of cycles, and fertile window length tended to be invariant regardless of cycle characteristics.

Importantly for users, these generally free apps have a business model based on selling user information to marketers. Users should assume their information is not private when using these apps.

NFP-Specific Apps. These apps are designed for use with one or many specific NFP methods. Most allow charting of symptoms but do not interpret the symptoms to define a fertile window (e.g., Read Your Body, Fertility Friend). A few apps do employ specific algorithms to define the fertile window (e.g., PeakDay, Chart Neo, FEMM).

A good NFP-specific app should (1) either not predict the fertile window (leaving interpretation to the trained user) or employ a predictive algorithm based on an evidence-based NFP method, (2) be developed and/or supported by NFP-knowledgeable researchers, (3) provide education on its use or links to educational resources, and (4) protect user data.

To date, only two apps have evidence of effectiveness to avoid pregnancy. The DOT app uses the menstrual cycle start day to predict the fertile window and, when combined with optional condom use in the fertile window, has a typical effectiveness unintended pregnancy rate of 5% in a US cohort of regularly cycling women (Jennings et al. 2019). DOT has US FDA approval as a contraceptive but is not commercially available today.

Natural Cycles is an approved contraceptive in both the US and EU and employs a temperature-only proprietary algorithm to define the fertile window. While clinical evidence in support of its use to avoid pregnancy demonstrates an 8–9% unintended pregnancy rate, the method is complicated by the fact that the app recommends the use of barriers rather than abstinence in the fertile window (Berglund Scherwitzl et al. 2017).

Since both apps encourage the use of barriers in the fertile window, they cannot be properly categorized as an NFP app; NFP requires periodic abstinence if avoiding. A study comparing the app-defined fertile window of natural cycles to an estimated biologic fertile window defined by cervical mucus illustrated that natural cycles declared the fertile window closed before the mucus-based fertile window was closed in up to 38% of cycles (Manhart and Duane 2022).

The panel felt NFP-specific apps needed high-quality studies to establish their effectiveness since several unexamined factors may render a specific method more or less well-adapted to app use. These factors include defining the extent of training required to use the method effectively and to what degree that training can occur within the app. Manhart (2020) demonstrated in an app utilizing the symptothermal method that those who used the app without training were significantly less persistent in their use and recorded daily data on significantly fewer days than those who had been trained on the method.

Hormone-Tracking System Apps. These are intended for use with fertility testing devices or tools. Several systems utilize quantitative measures of urinary metabolites of one or more of the four major reproductive hormones. Further discussion of these continues in the next section.

The popularity of menstrual-tracking apps holds the promise of a large data set to characterize and study the menstrual cycle across range of demographic cohorts. However, a review of 20 tracking apps each with over 1 million downloads revealed a lack of standardized language in describing and characterizing menstrual cycle events and experiences (Adnan et al. 2021) Thus, the current data from these apps, while voluminous, may not be useful for studies of the fertile cycle. Development of a standardized database that multiple apps can contribute to may be valuable.

The panel identified these priorities for future work:

  • Effectiveness data employing NFP-specific apps when used to avoid pregnancy or achieve pregnancy from well-designed studies.

  • Development of simple database that allows collection of cycle data from multiple NFP specific apps. Once assembled, such a database could be used for sophisticated analysis approaches (e.g., hidden Markov modelling) to gain further insights into predicting cycle characteristics.

New Hormonal Technologies for Monitoring the Fertile Signs

It has long been thought that quantitative analysis of reproductive hormone metabolites in urine will lead to critical insights on the fertile cycle, improve the clinician's ability to diagnose and treat subfertility/infertility, and make use of NFP easier and more accurate.

Today, at least four at-home quantitative monitoring systems are commercially available: Proov, Inito, OOva, and Mira. All these systems have US regulatory clearance for use as an aid to conception; they predict and confirm ovulation with accuracy considered equivalent to a predicate device.

Proov measures urinary estrone-1 glucuronide (E1G), luteinizing hormone (LH) (specifically the beta subunit), follicle-stimulating hormone (FSH), and pregnanediol glucuronide (PdG). FSH is detected via a separate stick; the other hormones are read on a single stick. A validation study of 40 women demonstrated ovulation prediction (by LH) and confirmation (by PdG) was accurate with high specificity and sensitivity (Wegrzynowicz, Eyvazzadeh and Beckley 2024). The mean fertile window in this cohort was 5.3 days. There are currently no algorithms or rules for the use of Proov monitoring to avoid pregnancy.

Inito measures urinary estrone-3 glucuronide (E3G), LH, and PdG metabolites by employing a lateral flow device that attaches to a smart phone camera. Validation studies in comparison to ELISA serum demonstrate high correlation (Pattnaik et al. 2023). The major drawback is pragmatic; the device cannot attach to a phone without removing the phone case.

Oova measures E3G, LH, and PdG; LH and PdG are measured in one strip, estrogen in a separate strip. Results are captured in the accompanying app via smartphone camera. Hill, Woodland and Divaraniya (2023) demonstrated the combination of age and a single-day measurement of LH and PdG could accurately predict the cycle phase and cycle day of that woman with 95% accuracy.

Mira measures E3G, LH, PdG, and FSH using a combination of test strips. Measures of E3G and LH have been compared to Clearblue qualitative strips and shown good correlation (Bouchard, Fehring and Mu 2021) A validation study comparing hormone values to ultrasound observed ovulation and serum hormone values is underway (Bouchard, Yong and Doyle-Baker 2023).

Quantitative testing is providing new insights on menstrual cycle hormone patterns. For example, in comparison studies with qualitative testing among postpartum and perimenopausal women, the women in these transition periods have lower estrogen levels and have higher LH surges in comparison with normal cycling women (Bouchard et al. submitted).

In addition, evidence is emerging that every woman has distinct daily levels of reproductive hormones. The spread of individual values on any given day is wide in comparison with the group mean or median values. This may suggest subgroups within the traditionally recognized groups (normal cycling, postpartum, perimenopause, PCOS, etc.) may be present. Further testing and validation are needed before we understand how these observations may impact clinical practice or use of NFP.

While quantitative hormone testing may provide more accurate ways to define the fertile window and more accessible information for diagnosis and management of sub-fertile conditions, much work remains to establish the evidence and demonstrate cost-effectiveness of these tools relative to alternatives, particularly among healthy regularly ovulating women.

The panel identified these priorities for future work:

  • Development of a large database employing quantitative hormone measures to provide new insight into cycle patterns, sub-types of various infertile conditions (e.g., PCOS), and transition periods.

  • Establish/validate the accuracy of quantitative hormone monitoring systems to identify i) the day of ovulation, and ii) the fertile window.

  • Comparative studies of quantitative hormone methods with other evidence-based methods to avoid/achieve to establish the benefit dimension (effectiveness, ease of use, cost, etc.).

The Impact of NFP on Marital Relations

Several studies have examined the perceived impact of NFP use on marital relationships, but nearly all suffer from small size, selection and/or reporting bias, and inconsistent measurement tools (reviewed in Manhart and Fehring 2021). Nevertheless, NFP users consistently state improved knowledge of their fertility, communication, self-control/self-mastery, increased intimacy, and spiritual well-being. Further, while abstinence is commonly recognized as challenging at times, a substantial majority feel the use of NFP has improved their marriage.

In the few studies comparing NFP with contraceptive users, NFP users tended to have significantly higher scores in measures of self-esteem, marital satisfaction, well-being, intimacy, and overall relationship functioning (Tortorici et al. 1979, Fehring and Kurtz 2002; Barroilhet et al. 2018)

Four population-based studies employing various waves of the National Survey of Family Growth demonstrate that ever-use of NFP (i.e., current or prior use) is associated with reduced odds of divorce when compared to never-use (Fehring 2013, 2015; Manhart and Fehring 2021; Manhart and Fehring 2023). In contrast, ever-use of common contraceptives (oral contraceptives, condom, male or female sterilization) was consistently associated with higher odds of divorce compared to never-use of the family planning methods (Manhart and Fehring 2021; Manhart and Fehring 2023).

Manhart and Fehring (2023) demonstrated that the odds of divorce associated with family planning choice were greater than the odds associated with traditional risk factors for divorce (low income, education or early age at marriage).

The panel identified these priorities for future work:

  • Examination of marital dynamics in cohorts using/not using NFP for varying lengths of time (e.g., newly married, married <5 yrs, 5–10 yrs, 10–15 yrs, > 15yrs).

  • Studies on fertility knowledge – validation of fertility knowledge measurement, and comparison of fertility health knowledge between users of NFP versus contraceptive users.

  • Extend the comparisons between family planning choices (NFP, contraception) to include validated measures of sexual function, STD rates, experiential dialogue, etc.

Discussion

While the meeting articulated several critical areas worthy of further research, an overarching concern among the panel is the lack of funding to conduct important research related to NFP. Most researchers interested in furthering the evidence supporting NFP are in organizations or institutions with limited financial means.

Finding creative ways to collaborate with corporate partners with FemTech products that do not create ethical dilemmas, identifying new sources of financial support, and/or crafting grant proposals that better align with current secular priorities will all need to be investigated.

Acknowledgements

Major financial support for this meeting was provided by the Natural Family Planning office of the United States Conference of Catholic Bishops, Catholic Medical Association, Marquette University Institute for Natural Family Planning, and the Couple to Couple League Fertility Science Institute. Additional support was provided by BOMA USA, FEMM, and the American Association of Pro-Life OBGYNs (AAPLOG). We thank these sponsors for their generosity.

Biographical Notes

Richard J. Fehring, PhD RN FAAN, is a professor emeritus and director of the Marquette University College of Nursing Boland Institute for Natural Family Planning. He received his master and doctorate in nursing from Catholic University of America and baccalaureate degrees in biology and nursing from Marquette University. He is also a science consultant to the Department of Natural Family Planning US Conference of Catholic Bishops.

Michael D. Manhart, PhD, received his PhD in microbiology from the University of Cincinnati College of Medicine. He had a long career in research and development with Procter & Gamble. In July 2009, he was appointed executive director of the Couple to Couple League (CCL) and led the organization until 2016. He currently serves as Board Chair and senior scientific consultant for CCL and is a member of the FACTS Board of Directors.

Data Availability: N/A

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding: The authors received no financial support for the research, authorship, and/or publication of this article.

Ethical Approval: There are no human participants in this article and informed consent is not required.

ORCID iDs: Michael D. Manhart https://orcid.org/0000-0003-1727-1846

Richard J. Fehring https://orcid.org/0000-0001-9071-4813

Invited Panelists: Amy Beckley, PhD, Founder and CEO of Proov, USA

Thomas Bouchard BSc, MD, PhD (Student), MMCP, Canada

Marguerite Duane, MD, Executive Director of FACTS about Fertility, USA

Rene Ecochard MD, PhD, Lyon, Fance

Richard Fehring, PhD, RN, FAAN, Emeritus professor Marquette University Boland Institute for Natural Family Planning, USA

Nefeli Malliou-Becher, MD, Department of Gynecological Endocrinology and Fertility Disorders, Heidelberg University, Germany

Michael D. Manhart, PhD, Fertility Science Institute, Couple to Couple League, USA

Maria Meyers, MD, MMCP, Jefferson County Health Department, Birmingham, Alabama, USA

Qiyan Mu, PhD, RN, Nurse scientist, Clement J. Zablocki VA Medical Center, USA

Rachel Peragallo Urrutia, MD, Associate Professor of Obstetrics and Gynecology at the University of North Carolina, Chapel Hill, USA

Bruno Scarpa, PhD, Professor of Statistics and Data Mining at the University of Padova, Italy

Theresa Stujenske, BSN, PhD, Assistant professor, Duquesne University School of Nursing, USA

Craig Turczynski, Ph.D, BOMA-USA, FEMM, USA

Pilar Vigil MD, PhD, Professor, Pontifical Catholic University of Chile, Chile

Andrea Killian Wegrzynowicz, PhD, Postdoctoral Fellow, Department of Obstetrics and Gynecology, University of Wisconsin-Madison, USA

Paul Yong, MD, PhD, FRCSC, Vancouver, Canada

Shahpar Najmabadi, PhD, MPH, University of Utah, USA

Mary Schneider, PhD, APRN, FNP-BC, MMCP, Director Marquette University College of Nursing Boland Institute for Natural Family Planning, USA

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