Fertility awareness-based methods of pregnancy prevention

INTRODUCTION — Fertility awareness-based (FAB) methods for preventing pregnancy are based upon the physiologic changes during the menstrual cycle and the functional lifespan of sperm and ova. The patient is educated to understand when they are in their fertile period so they can then avoid vaginal intercourse or use a coital-dependent contraceptive method, such as a condom. These methods are also referred to as natural family planning. FAB methods are best used by motivated individuals whose partners also support the use of this contraceptive approach.

This topic will discuss different FAB methods, candidates, counseling points, and method use. In the text, we will use the terms "woman," "women," or "patient" to describe those who use female contraceptive methods. However, we recognize that not all people capable of pregnancy identify as women, and we encourage the reader to consider the specific counseling needs of transgender men. Clinicians should ask all patients who identify as male about their contraceptive needs as well.

Related content on contraceptive selection is presented separately. (See "Contraception: Counseling and selection".)

In this topic, when discussing study results, we will use the terms "woman/en" or "patient(s)" as they are used in the studies presented. However, we encourage the reader to consider the specific counseling and treatment needs of transgender and gender diverse individuals.

WHAT IS FERTILITY AWARENESS-BASED CONTRACEPTION? — FAB methods, also called "natural family planning," involve identifying the fertile days of the menstrual cycle using a combination of cycle length and physical manifestations of ovulation (change in cervical secretions, basal body temperature) and then avoiding sexual intercourse or using barrier methods on those days [1]. These methods can also be used in reverse to improve the chance of conception by couples attempting to conceive. (See 'Physiology of fertility awareness-based methods' below.)

FAB methods rely on the following [2,3]:

●The periodicity of fertility and infertility

●A single ovulation each cycle

●The limited duration of viability of the ovum, which can only be fertilized 12 to 24 hours after release

●The limited duration of viability of sperm (three to five days in cervical mucus and the upper genital tract)

●A woman's ability to monitor cycle length and/or cycle-related symptoms and signs, such as changes in cervical mucus

Studies using sensitive hormonal tests and ultrasound have established that a woman is fertile from five days before ovulation to the 24 hours after ovulation (ie, six days total per cycle) [4]. Identifying the six-day fertile window is the critical component of any FAB method. The probability of pregnancy from unprotected intercourse during this period is as follows (figure 1):

●Five days before ovulation – 4 percent

●Two days preceding ovulation – 25 to 28 percent

●During the 24 hours after ovulation – 8 to 10 percent

●For the remainder of the cycle – 0 percent

PATIENT SELECTION

Ideal candidates — Potential candidates for FAB methods are individuals who choose to use them for health or personal reasons, are able to comply with FAB method requirements, and will abstain from sexual intercourse or use barrier methods on fertile days. The most appropriate candidates for FAB methods are those who can communicate with their partners and whose partners are willing to support use of this method [1,3].

Variables to consider in counseling about FAB methods are a couple's motivation to use the method consistently and correctly, the individual's desire to monitor fertility signs, and their partner's desire to be involved. Certain aspects of FAB methods, such as monitoring physiologic changes or shared responsibility for contraception, may be unappealing to some individuals but be seen as a positive to others.

Resource-limited settings — Global studies from resource-limited settings report that motivated patients who meet the criteria for FAB method use can successfully use a FAB method [5,6]. FAB methods may be the only available options in some areas. Worldwide FAB use has been estimated at 3.6 percent [2]. While the Standard Days Method and the TwoDay Method were designed for females with limited resources because they do not require additional tools, these methods can be used by individuals across all socioeconomic circumstances. (See 'Standard Days Method' below and 'TwoDay Method' below.)

Relative contraindications — Patients who desire a highly reliable contraceptive, do not have regular menses, are unable to track their menses or physiologic changes, do not have a supportive partner, and/or desire protection from sexually transmitted infections are not ideal candidates for FAB methods [1]. Relative contraindications include:

●Irregular cycles – As most FAB methods involve tracking menses to identify the fertile window, patients with irregular cycles for any reason are suboptimal candidates for FAB use. Such patients include those with recent menarche, discontinuation of some hormonal contraceptives, polycystic ovarian syndrome or oligoovulation, and perimenopause [1,7,8].

●Interruption of cycles – Pregnancy interrupts the cyclic release of hormones that results in the menstrual cycle. Thus, people who have been pregnant, including those with pregnancy loss, abortion, or delivery, do not know when their hormonal cycles, and thus ovulation, will resume.

●Inability to track physiologic changes – Patients who are unable or unmotivated to track physiologic changes in cervical secretions and basal body temperature are advised to consider other contraceptive methods. Such patients can include those with intellectual disability, adolescents, and those in unstable or chaotic environments (eg, homelessness).

In addition, the ovulation, TwoDay, and symptothermal methods are not appropriate for those unable to interpret their fertility signs, such as individuals with persistent reproductive tract infections that alter vaginal secretions.

●Lack of supportive partner – As a key component of FAB methods is abstinence or temporary contraceptive use during the fertile window, FAB methods will not work for patients whose partners will not comply.

EFFICACY

Overall — Typical-use pregnancy rates approach 25 percent for FAB methods combined (figure 2) [1,9]. There are no high-quality randomized trials comparing efficacy of different FAB methods [10,11]. Typical-use unintended pregnancy rates range from 2 (symptothermal method) to 23 percent (ovulation method) [9]. Reported perfect-use failure rates during the first year range from 0.4 to 5.0 percent, which appear comparable across methods. The disparity between perfect- and actual-use pregnancy rates is greater for methods that require more user action than for simpler ones. The population studied may impact the typical-use failure rate.

Learning time impact on efficacy — The time needed to learn the method and use it correctly must be considered when assessing FAB method efficacy.

●Impact of learning phase – Some early efficacy studies of FAB methods (specifically of the cervical mucus or ovulation method and the symptothermal method) enrolled study participants only after they had completed a learning phase, typically consisting of three cycles of use, while others enrolled participants from the day they started using the methods. Since failure rates are highest during the early cycles of use, when patients are enrolled can be an important factor in study outcome [12]. Subsequent studies of the Standard Days Method (SDM) and the TwoDay Method enrolled individuals as soon as they started using the methods. These studies reported that over 20 percent of couples had intercourse during their fertile days when they first learned to use a method but that this percentage dropped sharply during the first three months and continued to decline during the first year of use [13].

●Impact of ease of use – Methods that are easier to use than the ovulation and symptothermal methods also may result in regular use and thus greater effectiveness [14]. For example, Clue Birth Control (formerly Dot) and Natural Cycles are easily used by individuals with consistent access to a mobile phone [15,16].

Clue Birth Control (previously called Dot) and Natural Cycles, incorporate algorithms derived from large databases into mobile phone apps. These apps have been approved by the Federal Drug Administration (FDA) for use by individuals ages 18 and over who meet criteria for using them. These methods have perfect-use failure rates of 3 and 5 percent and typical-use failure rates of 8 and 2 percent, respectively, and are easily used by individuals with consistent access to a mobile phone [15,16].

Traditional fertility awareness-based methods

●Standard Days Method – In an observational study that taught nearly 500 women the SDM with a CycleBeads teaching device and followed them for up to 13 cycles, the unintended pregnancy rate for perfect use was <5 per 100 women per year [17]. The typical-user pregnancy rate of the SDM was 12 per 100 women per year.

●Ovulation methods – In a prospective multi-country study of over 850 women who were taught the ovulation method, the correct-use failure rate was 3 per 100 women per year, and the typical-user failure rate was 23 per 100 women per year [18,19]. The large difference between correct and typical use reflects the complexity of learning and using the method correctly, as well as the choice of some couples to have unprotected intercourse on fertile days. One study of a streamlined patient counseling program reported a lower typical-use failure rate of 16 per 100 users at 21 months [20].

●TwoDay Method – A prospective, multisite efficacy study of the TwoDay Method followed 450 women for up to 13 cycles of use [21]. The first-year correct-use pregnancy rate was 3.5 per 100 women per year, and the typical-use pregnancy rate was <14 per 100 women per year. The lower typical-use failure rate of the TwoDay Method compared with the cervical mucus or ovulation method is probably due to its simplicity. Individuals may find it easier to learn and use and thus are more likely to use it correctly.

●Symptothermal method – Efficacy studies indicate that this method has a correct-use first-year pregnancy rate of 2 per 100 women per year and a typical-user pregnancy rate between 13 and 20 per 100 women per year [22-24]. The wide range in failure rates reflects differences in study designs. The large difference between correct- and typical-use failure rates probably reflects the complexity of learning and using the method correctly and the issues around avoiding unprotected intercourse on fertile days.

●Fertility monitor (Marquette) method – In a 24 month prospective study, 663 non-breastfeeding women who desired to avoid pregnancy used a university-based online web tracking system to record their cervical mucus changes, hormone-monitoring test results, or both [25]. The unintended pregnancy rate for typical use was 15 percent while the perfect-use rate was 2 percent. Study participants using the electronic fertility monitor alone had the lowest unintended pregnancy rate (6 percent) compared with those using only cervical mucus monitoring (18 percent) or those using both fertility indicators (19 percent).

Computer and phone applications (apps) — Studies evaluating apps for pregnancy prevention are limited. Clue Birth Control (previously called Dot) and Natural Cycles incorporate algorithms derived from large databases into mobile phone apps. These apps have been approved by the Federal Drug Administration (FDA) for use by individuals ages 18 and over who meet criteria for using them [26,27].

●Natural Cycles app – A prospective observational study of the Natural Cycles app that included over 18,500 woman-years of data reported a typical-use Pearl Index (PI) of 6.9 pregnancies per 100 woman-years (95% CI 6.5-7.2), a 13-month typical-use pregnancy rate of 8.3 percent, and a 12-month discontinuation rate of 54 percent [15]. Study limitations included lack of data on the methodology or assumptions for the app algorithm and limited data on episodes of sexual activity (ie, exposure). An observational study of Natural Cycles app users reported lower typical-use one-year PIs for those who switched to the Natural Cycles app from a less effective contraceptive method (condoms: PI 3.5±0.5) compared with individuals who switched from more effective methods (prior oral contraceptive pill use: PI 8.1±0.6) [28].

●Clue Birth Control – A prospective cohort study of 718 women using Clue Birth Control (formerly Dot) followed established guidelines for contraceptive efficacy studies and reported a 13-month typical-use failure rate of 5 percent [16].

COUNSELING POINTS

●Safety – There is no evidence of direct harm from use of FAB methods [29]. However, the harm from unintended pregnancies needs to be considered when evaluating any contraceptive method. Individuals with certain medical conditions should be advised that sole use of barrier methods for contraception and behavior-based methods of contraception may not be the most appropriate choice because of their relatively higher typical-use rates of failure (figure 2).

Because unintended pregnancies among couples who use FAB methods usually result from having intercourse at the beginning or end of the fertile time within a cycle, concerns have been raised about the risk of congenital anomalies or poor pregnancy outcomes due to aged ovum or sperm. There is no evidence to support these concerns. Fertilization of aging gametes (ie, age from ejaculation or ovulation) is not associated with major congenital anomalies or Down syndrome [30]. A prospective study that evaluated rates of spontaneous abortion, low birth weight, or preterm birth among women who had an unintended pregnancy while using a FAB method versus women who had intended pregnancies reported no significant differences in these outcomes [29]. An exception is that, in one prospective study, women with a history of spontaneous abortion had a greater chance of having another spontaneous abortion when conception occurred very early or late in the fertile time (23 versus 10 to 15 percent) [29].

●Benefits – Benefits of FAB methods include:

•No local or systemic adverse effects

•No or minimal cost

•No delay in return of fertility

•No interactions with other drugs

●No sexually transmitted infection (STI) protection – FAB methods do not reduce risk of STI transmission.

•(See "Prevention of sexually transmitted infections".)

●Barriers to FAB use – Surveys and behavioral research worldwide indicate that individuals who choose FAB methods do so because of their concerns about side effects and health consequences of other contraceptive methods. Religious constraints appear to play a small part in their method choice [31]. Although many people have concerns about non-FAB methods of pregnancy prevention, most have not embraced FAB methods. Only an approximate 1 percent of women in the United States use FAB contraception [32], and 3.6 percent use it worldwide [2]. Possible explanations include lack of information, inconvenience, and concerns about efficacy (high typical-user failure rate):

•Lack of information – The lack of readily available patient information on FAB methods is likely related to at least three factors: (1) the absence of a profitable product to advertise and sell, (2) provider concern that these methods are not as effective as other choices, and (3) the amount of time needed to counsel patients [33-35]. Studies including both physicians and nurse-midwives have shown that relatively few providers routinely include information about FAB methods in their family planning discussions with patients. As an example, a survey of approximately 500 physicians in the United States found that one-third did not mention FAB methods to their patients at all, while 40 percent mentioned them only to selected women [34]. When asked by a patient for information about a FAB method, most physicians described either calendar rhythm or basal body temperature, which are among the least effective FAB methods (see 'Historical methods no longer used' below). In another study, nurse-midwives offered little information about FAB methods based on their perception that these methods were not effective or were inappropriate for their patients [35]. A recent survey of Title X service providers found that providers were either neutral or negative toward FAB methods, considered them inappropriate for most patients, and rarely offered them unless patients specifically requested them [36].

•Convenience – FAB methods can be labor-intensive for the clinician because of the time required for choosing the most appropriate method for an individual and for teaching them the method. These methods also require ongoing effort on the individual's part and impact spontaneity in sexual relations. Newer FAB methods, as well as digital applications (smartphone apps) and devices, are relatively easy to incorporate into regular clinical services, and use may increase interest and availability.

•Duration of abstinence or additional contraception – While the fertile window is typically six days, some FAB methods include longer periods of abstinence or condom use to reduce the risk of pregnancy. Abstinence or condom use for periods of 12 to 17 days have been reported and may decrease the desirability of FAB methods [18,37].

PHYSIOLOGY OF FERTILITY AWARENESS-BASED METHODS

Fertile window — Studies using sensitive hormonal tests and ultrasound have established that a woman is fertile from five days before ovulation to the 24 hours after ovulation [4]. The probability of pregnancy from unprotected intercourse during this period is as follows (figure 1):

●Five days before ovulation – 4 percent

●Two days preceding ovulation – 25 to 28 percent

●During the 24 hours after ovulation – 8 to 10 percent

●For the remainder of the cycle – 0 percent

These probabilities are related to the limited viable lifespan of the sperm inside the woman's reproductive tract (not more than five days) and to the even more limited viable lifespan of the ovum following ovulation (less than 24 hours). As a result, the fertile window is no more than six days per cycle [4]. Predicting the onset and determining the end of the six-day fertile window are the critical components of a FAB method. This involves a combination of cycle length and physical manifestations of ovulation (change in cervical secretions, basal body temperature [BBT]).

Cycle length — In 95 percent of menstrual cycles, ovulation occurs in the four days before or after the midpoint of the cycle, and in approximately 30 percent of cycles, ovulation occurs at the exact midpoint of the cycle (eg, day 14 in a 28-day cycle, day 15 in a 30-day cycle) (figure 3).

A computer model that applied the probability of ovulation on any given day and the probability of conception before and after ovulation calculated that the fertile period in women with menstrual cycles of 26 to 32 days was on days 8 through 19 (cycle day 1 is the first day of the menstrual period) [37]. Subsequent modeling resulted in an algorithm that was applicable to cycle lengths of between 20 and 40 days and that was able to determine a variable fertile window depending on the pattern of cycle lengths [38]. The algorithm identified that intercourse was to be avoided for 11 to 13 days per cycle for any given patient, assuming couples had intercourse during menses. For individuals or couples who prefer to avoid intercourse during menses, the number of days of abstinence in a typical 28-day cycle would range from 15 to 20.

Cervical secretions — Abundant, clear, wet, stretchy cervical secretions occur immediately before, during, and immediately after ovulation; thus, the day of ovulation can be predicted by observing changes in vaginal discharge that occur over a typical 28-day menstrual cycle [39]. The sequence of change is menses; followed by no secretions for 3 to 4 days; followed by scant, cloudy, sticky secretions for 3 to 5 days; followed by abundant, clear, wet, stretchy secretions for the 3 to 4 days immediately before, during, and immediately after ovulation; and, finally, no secretions for 11 to 14 days, at which time the next menstrual period begins. The duration of these phases varies by cycle length and in individual women. While changes in characteristics of cervical secretions are of clinical interest, the critical feature of secretions for purposes of identifying the fertile window is their presence or absence [40].

The characteristics of cervical secretions during the menstrual cycle are affected by serum estradiol and progesterone concentrations. Before ovulation, estradiol produced by the developing follicle stimulates the production of cervical secretions that facilitate passage of sperm through the cervix and lead to functional maturation of sperm (capacitation) so that fertilization of the ovum is possible. Following ovulation, progesterone produced by the corpus luteum causes an abrupt change in secretions, which then inhibit sperm migration and capacitation.

Basal body temperature — In a normal menstrual cycle, BBT is approximately 0.5°F (0.3°C) higher in the luteal phase than in the follicular phase. The temperature rise begins 1 or 2 days after the surge in luteinizing hormone and the rise in progesterone concentrations and persists for at least 10 days. Temperature elevation identifies ovulation retrospectively and thus signifies the end, rather than the onset, of the fertile period. Viral infections that cause low-level rises in temperature can affect BBT [1].

CHOOSING A FERTILITY-AWARENESS BASED METHOD — The optimal FAB method is easy to use and minimizes the number of days that sexual intercourse must be avoided or practiced with a barrier contraceptive. Ultimately, the method that the patient and their sexual partner(s) will use correctly and consistently is the best one to choose. We review each of the FAB methods with the patient, and ideally their partner, and then provide detailed instruction on the method they ultimately select (table 1). We also discuss, at least briefly, other contraceptive options and their effectiveness (figure 2).

FERTILITY AWARENESS-BASED METHODS

Standard Days Method — The Standard Days Method (SDM) is a calendar-based method that determines fertile days using two sets of probabilities: the probability of pregnancy with respect to ovulation and the probability that ovulation occurs near the midpoint of the cycle. It is the easiest FAB method to teach and use and has the fewest days requiring abstinence or barrier contraception. The only instruction is to avoid unprotected intercourse from day 8 through day 19 of the cycle (12 days); the user may have unprotected intercourse on all other days.

SDM is appropriate for persons whose menstrual cycles are usually between 26 and 32 days (approximately 78 percent of cycles are within this range) [37]. Thus, individuals with polycystic ovary syndrome, adolescents whose cycles may be irregular in early postmenarche, breastfeeding persons with amenorrhea, individuals who have recently been pregnant, and those in the menopausal transition often are not good candidates [41,42].

Additional counseling points include the following:

●Initial cycle assessment – The first step in SDM counseling is assessing whether the method is appropriate for the individual. While it is not necessary for them to know their exact cycle length, a "yes" response to the two questions "Do your periods usually come approximately one month apart?" and "Do your periods usually come when you expect them?" is sufficient for this assessment [43].

The table provides guidance for initiating SDM use (table 2). Individuals who know when their last period started can begin using SDM immediately; those who do not know should wait until their next period begins. Individuals who were recently pregnant, breastfeeding, or using hormonal contraception should be asked about their recent and past menstrual history to determine whether SDM is appropriate for them and when to start it.

●Monitor cycle length – Individuals using SDM should monitor their cycle length since some people have less regular cycles than they initially believed [31]. SDM is less effective in persons with frequent cycles outside the 26 to 32 day range [37]. Therefore, individuals who have two or more cycles longer than 32 days or shorter than 26 days in a 12 month period should be encouraged to use another method [44].

●Abstinence or barrier method – Abstinence or a barrier contraceptive method is used from day 8 through day 19 of the cycle (12 days); the user may have unprotected intercourse on all other days.

●Use of tracking aids – Most people can learn to use SDM in approximately 20 minutes. We suggest use of a visual tool, such as CycleBeads, a string of 32 color-coded beads (figure 4), or an iCycleBeads software application (figure 5), to track cycle days, visually indicate the fertile days (days 8 to 19), and monitor cycle lengths to ensure they are between 26 and 32 days. Several studies have confirmed that CycleBeads is a critical component of teaching and correctly using SDM [45]. CycleBeads is available through some family planning clinics and retailers; iCycleBeads software applications are available for download to iPhone and Android devices.

Regardless of which tool is selected, tracking begins with the first day of the menstrual period each cycle. A marker helps the user track the cycle day and identify whether they are fertile that day. Users are counseled to avoid unprotected intercourse when the marker is on a day identified as fertile.

Cervical mucus or ovulation method — The cervical mucus or ovulation method requires individuals to evaluate their cervical secretions several times each day to decide whether the day is a potentially fertile day; thus, it takes more time to teach and learn than other methods. One advantage is that persons with cycles <26 or >32 days can use this method, unlike the SDM above. Unprotected intercourse is avoided on potentially fertile days plus some additional days as specified by method rules (see below). As a result, cervical mucus method users need to avoid unprotected intercourse for approximately 14 to 17 days each cycle [46]. Examples of cervical mucus methods are the TwoDay, Billings ovulation, and Creighton Model methods. Cervical mucus can also be assessed using a variety of devices. (See 'Device-assisted methods' below.)

TwoDay Method — The TwoDay Method is based on assessment of cervical secretions [40]. For the TwoDay Method, the mere presence or absence of cervical secretions is considered sufficient to determine the fertile period. TwoDay Method users are counseled to avoid unprotected intercourse on all days that they note the presence of secretions and on the first day following a day with secretions. The presence of secretions conforms sufficiently to the actual fertile window so that further evaluation of the secretions' characteristics is not necessary.

●Teaching – Most people can learn to use the TwoDay Method in a single counseling session based on a validated teaching tool and checklist, which is available online, when they present for family planning [47,48]. They learn what to expect in terms of presence and absence of secretions in a typical menstrual cycle: no secretions immediately following menses, secretions (of various types) beginning a few days after menses and continuing for several days, and absence of secretions again until after the next menses.

●Monitor cervical secretions – TwoDay Method users monitor the presence or absence of secretions and then ask themselves two questions: "Did I have any secretions today?" and "Did I have any secretions yesterday?" (algorithm 1). If any secretions were noted today or yesterday, today is a potentially fertile day, and users should avoid unprotected intercourse. If the user did not notice any secretions today or yesterday (ie, two consecutive days with no secretions), their probability of conceiving today is very low, and unprotected intercourse is permitted.

Learning to recognize whether or not they have secretions at the vulva is critical for TwoDay Method use. Users are encouraged to make these observations two times each day: once during the afternoon and once before going to bed at night. (If they have intercourse at times other than at night or early in the morning, they should adjust the times of observation accordingly to avoid confusing the presence of semen with secretions). As with the Billings or Creighton methods discussed below, users of the TwoDay Method note secretions on toilet paper or underwear or by the feel at the vulva. Users typically chart the presence or absence of secretions and menses and thus identify their fertile days (figure 6). Some women prefer to use an app, 2Day Method, to record their secretions [49]. Women can learn to use the TwoDay Method anytime during a cycle [47].

●Abstinence or barrier method – Patients using the TwoDay Method avoid intercourse or use a barrier method on days when secretions are present and for an additional day following a day with secretions. An analysis of almost 4000 cycles in women using the TwoDay Method found that the mean length of the identified fertile period was 13 days; thus, users needed to avoid unprotected intercourse for approximately 13 days of each cycle (range 10 to 14 days) [21].

Billings and Creighton methods — The Billings ovulation method is the oldest method of observing cervical secretions for fertility awareness. A variant on the Billings ovulation method, the Creighton Model, requires that the woman score the secretions according to a multicharacteristic scale [50]. Based on the rules below, the user avoids unprotected intercourse for approximately 14 to 17 days of each cycle.

●Teaching – Most method users require several instructional sessions to recognize the pattern of secretions in a typical menstrual cycle. In these sessions, they learn to observe, record, and interpret their cervical secretions, paying particular attention to the color, elasticity, abundance, and viscosity.

Learning to observe secretions at the vulva and evaluate them is critical for using this method. Method users are encouraged to make these observations several times each day, preferably prior to each urination. Techniques include touching the vulva with the fingers or toilet paper to collect secretions and assess their characteristics, noting secretions on underwear, and simply "feeling" wetness at the vulva.

●Monitor cervical secretions – Various approaches to recording observations have been developed to help method users become familiar with their fertile patterns over time. Commonly, users use a chart on which they mark days of menses, days with secretions (including characteristics of secretions), and days when pregnancy is likely. An example of a patient record is shown in the table (table 3).

●Abstinence or barrier method – Patients using the Billings ovulation or Creighton methods are counseled to avoid unprotected intercourse:

•During menses (because of the possibility that menstrual bleeding could obscure the presence of secretions, particularly in short cycles)

•On preovulatory days following days with intercourse (even if there are no secretions present because of the possible confusion with semen)

•On all days with wet, slippery, transparent, or stretchy secretions consistent with ovulation

•Until four days past the last day with wet secretions

Based on these rules, the user avoids unprotected intercourse for approximately 14 to 17 days of each cycle.

Multimodal methods

Symptothermal method — The symptothermal method is based on changes in cervical secretions and basal body temperature (BBT) produced by hormonal changes during the menstrual cycle [51]. The presence of wet, slippery, transparent, or stretchy cervical secretions is the primary indicator of the beginning of the fertile phase of the cycle, and BBT elevation is the primary indicator of the end of the fertile phase.

The symptothermal method requires individuals to observe and evaluate their cervical secretions several times each day, take their temperature with a BBT thermometer (a thermometer calibrated to be easy to read in the temperature range of interest) each morning before rising, and record and interpret these findings to determine whether the day is a fertile day. Some symptothermal method users also check the position and feel of the cervix.

This method can be used by those with short, long, or irregular cycles. It is cumbersome and has no significant advantages over other methods.

●Teaching – It is critical that users of the symptothermal method learn to observe, evaluate, and record their secretions and to take and record their BBT. Most method users require several instructional sessions to use the symptothermal method. They record their temperatures on a chart and attempt to identify the temperature rise associated with ovulation. Three higher temperatures following at least six days of lower temperatures indicate that ovulation has occurred.

●Monitor cervical secretions and BBT – Individuals are encouraged to observe secretions before each urination and to take their temperature each day before rising. They record their observations of menses, secretions (and their characteristics), and temperature on a chart (figure 7).

●Abstinence or barrier method – Users of the symptothermal method need to abstain or avoid unprotected intercourse for approximately 12 to 17 days each cycle. Specifically, users are counseled to avoid unprotected intercourse on potentially fertile days, including:

•All days with secretions

•All preovulatory days following days with intercourse (even if there are no secretions present because of the possible confusion with semen)

•Until three days of higher temperatures have followed at least six days of lower temperatures or the fourth day after the last day with wet secretions, whichever happens later

Device-assisted methods — There are several devices that can help individuals identify their fertile days. These include mini microscopes that allow observation of ferning of saliva or of cervical mucus (eg, PG 53, PC 2000, Maybe Baby) and handheld computers that measure cycle length and correlate the day of the cycle with BBT (eg, Babycomp, Ladycomp, Bioself 2000, Cyclotest 2 Plus). Research to evaluate the effectiveness of some of these devices to prevent pregnancy suggests that mini microscope-type devices would have high failure rates [52]. Studies of mini microscopes have not found them to be effective in helping prevent pregnancy. Studies that have assessed the contraceptive efficacy of computing devices are inconclusive [53-55]. In one study, Persona, which measures urinary hormone metabolites to identify the fertile days, had a failure rate of 6 percent with correct use [56]. The cost of these devices can be prohibitive.

Fertility monitor (Marquette) method — Studies of individuals using the Clearblue Easy Fertility Monitor indicate that the device provides accurate information about the fertile window, particularly when used with a calendar-based formula to double check the beginning and end of the fertile phase. This approach to identify the fertile window is referred to as the Marquette Model and is often combined with a tracking system and cervical mucus assessment [57-59]. Typical-use unintended pregnancy rates are approximately 15 percent [25].

Computer and phone applications (apps) — The exponential growth and popularity of computer and smartphone applications (apps) related to fertility suggest that clinicians should be prepared to guide their patients in identifying and selecting apps that provide accurate information and are appropriate for particular needs. Some "fertility apps" are essentially digital platforms that support an individual's use of an existing FAB method, such as the symptothermal method, the ovulation method, or SDM. These apps replace the traditional paper and pencil charts associated with these methods. If an app accurately represents the FAB method on which it is based, it can be assumed that its effectiveness for pregnancy avoidance would be the same as that for the underlying method. However, in a study that evaluated 95 fertility apps, over one-half (55) were excluded from the study because they either did not identify an evidence-based FAB method or they included a disclaimer that the app was not intended to avoid pregnancy [60]. Of the remaining 40 apps, 4 accurately represented the symptothermal method (commercial names Sympto, LilyPro, Lady Cycle, and nfNFP.net), and 1 accurately used SDM (commercial name CycleBeads). A subsequent systematic review of 22 studies evaluating smartphone apps for contraception reported that the majority of apps contained incomplete information [61]. Lastly, a review of 18 studies concluded that, while app users value products that are accurate and scientifically based, health professionals are rarely involved in app design, and there is little regulation of these products [62].

Other fertility apps use algorithms, the majority of which are proprietary and have not been methodologically evaluated in the peer-reviewed literature. The Natural Cycle app, approved for marketing to United States consumers in 2018, uses an algorithm to predict fertile days based on input of BBT data and dates of menstruation, with optional input of luteinizing hormone test results [63]. Another app, Clue Birth Control (previously called Dot), uses an algorithm to predict fertile days based on period start dates. The Dot algorithm was developed from a simulation analysis of data from two cohort studies and a prospective trial [38]. The efficacy study of Dot follows standard guidelines for determining perfect and typical use of contraceptive methods [19] and has been registered with the United States National Institutes of Health [64]. Over 700 women were enrolled in the trial [65]. Dot was found to be 99 percent effective with perfect use and 95 percent effective with typical use. Clue Birth Control uses the upper bound of the confidence interval (CI) from the Dot trial as a more conservative estimate of effectiveness [16].

Lactational amenorrhea — Lactational amenorrhea is the educated use of exclusive breastfeeding in an amenorrheic woman for up to six months after delivery. (See "Contraception: Postpartum counseling and methods", section on 'Other'.)

Monitoring of cervical secretions is challenging for breastfeeding women because they may have continuous cervical secretions that do not indicate ovulation [41]. However, instructions have been developed for using the cervical mucus or ovulation method and the symptothermal method under these "special circumstances." (Refer to The Art of Natural Family Planning Postpartum Guide and Premenopause Guide available from the Couple to Couple League at https://ccli.org/.) A pilot study reported a FAB bridge for postpartum women to start with their first postpartum menses and until they are eligible to use SDM [66].

Basal body temperature trackers — Commercial products (eg, Baby Comp and Lady Comp) are available to assist patients in tracking their basal body temperature and provide information about the likelihood of conception throughout the menstrual cycle. However, neither the accuracy of the information nor the efficacy for pregnancy prevention have been confirmed in well-designed efficacy studies.

ROLE OF EMERGENCY CONTRACEPTION — We counsel all patients interested in avoiding pregnancy about the availability and use of emergency contraception methods. (See "Emergency contraception".)

HISTORICAL METHODS NO LONGER USED

●Calendar rhythm – In the early decades of the 20^th century, it was known that individuals were more likely to become pregnant at midcycle and that the luteal phase was of a more fixed length than the follicular phase [67]. The calendar rhythm method was developed based on this information.

This method requires the individual, prior to using the method, to determine the length of their last six cycles and then to subtract 18 from the number of days in their shortest cycle and 11 from the number of days in their longest cycle. This determines their fertile period when unprotected intercourse should be avoided. As an example, if their shortest cycle is 26 days and their longest cycle is 34 days, then their fertile period is from day 8 to 23.

While undoubtedly serving to prevent many unplanned pregnancies, calendar rhythm resulted in high failure rates because it required the user to maintain records of cycle length prior to and during method use, involved arithmetical calculations each cycle, had no eligibility criteria, and had poorly defined parameters. No well-designed efficacy trials of the calendar rhythm method have been conducted, and generally, it is not offered in clinical services today.

●Basal body temperature (BBT) – By midcentury, the importance of the biphasic BBT pattern in determining ovulation was recognized [68]. Since BBT elevation identifies the end of the fertile period rather than the onset, users of this method have to avoid unprotected intercourse from the beginning of the cycle until at least three days of elevated temperatures have occurred (ie, for well over one-half of the month). Thus, it is not a popular choice.

ONLINE RESOURCES FOR FERTILITY AWARENESS-BASED METHODS

●Under Title X, the US Department of Health and Human Services provides free online information about all contraceptive methods, including FAB methods.

●Standard Days Method and TwoDay Method – Information on the Standard Days Method and the TwoDay Method is available from the Georgetown University Institute for Reproductive Health at https://irh.org/twoday-method/.

●Cervical mucus or ovulation methods (Billings, Creighton)

•Information on the Billings ovulation method is available from Billings Life at https://billings.life/en/

•Information on the Creighton Model is available from the Creighton Model FertilityCare System at https://creightonmodel.com/

●Symptothermal method – Information on the symptothermal method is available from Fertility United Kingdom at www.fertilityuk.org.

●Marquette Model – Information on the Marquette Model is available from Marquette University at https://www.marquette.edu/nursing/natural-family-planning-model.php.

●The World Health Organization online content on contraception.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Contraception".)

SUMMARY AND RECOMMENDATIONS

●Description – Fertility awareness-based (FAB) methods, also called "natural family planning," involve identifying the fertile days of the menstrual cycle using a combination of cycle length and physical manifestations of ovulation (change in cervical secretions, basal body temperature [BBT]) and then avoiding sexual intercourse or using barrier methods on those days. (See 'Introduction' above and 'Physiology of fertility awareness-based methods' above.)

●Candidates – The most appropriate candidates for FAB methods are individuals who are motivated to track these methods, can communicate with their partners, and whose partners are willing to support use of these methods. Patients who are not ideal candidates for FAB methods include those who desire a highly reliable contraceptive, do not have regular menses, are unable to track their menses or physiologic changes, do not have a supportive partner, and/or desire protection from sexually transmitted infections (STIs). (See 'Patient selection' above.)

●Pregnancy rates – Typical-use pregnancy rates approach 25 percent for FAB methods combined (figure 2) [1,9], although this estimate includes pregnancies that occur when the user has not been counseled on a FAB method and may be uninformed about their fertility status during their cycle. Reported perfect-use failure rates during the first year range from 0.4 to 5.0 percent, which appear comparable across all FAB methods. The disparity between perfect- and actual-use pregnancy rates is greater for more complex methods than for simpler ones. (See 'Efficacy' above.)

●Risks and benefits – There is no evidence of direct harm from use of FAB methods. However, the harm from unintended pregnancies needs to be considered when evaluating any contraceptive method. Benefits of FAB methods include unlimited access and no or low cost. However, FAB methods do not protect against transmission of STIs. (See 'Counseling points' above.)

●FAB methods and selection – Individuals should choose a FAB method based on their preferences regarding the procedures involved in using each method and the number of days per cycle during which the user needs to avoid unprotected intercourse, while accounting for the specific constraints of the method. (See 'Choosing a fertility-awareness based method' above.)

•Standard Days Method – The Standard Days Method (avoid unprotected intercourse from day 8 through 19) is only appropriate for individuals with regular cycles of 26 to 32 days. It is the easiest FAB method to teach and use, and many individuals learn to use it without counseling through information available through web applications, such as iCycleBeads, that can be downloaded onto smart phones or tablets. The user abstains or uses a barrier method for 12 days, which is fewer days than for the ovulation or symptothermal methods. (See 'Standard Days Method' above.)

•TwoDay Method – TwoDay method users are counseled to avoid unprotected intercourse on days when they note cervical secretions and on the day after the day with cervical secretions. It is the easiest cervical secretion method to learn and perform. The TwoDay Method can be used by individuals with short, long, or irregular cycles. Users of the TwoDay Method abstain or use a barrier method for approximately 13 days each cycle. (See 'TwoDay Method' above.)

•Observation of cervical mucus – The cervical mucus or ovulation method requires individuals to observe and evaluate their cervical secretions several times each day and avoid unprotected intercourse based on their findings. This method may be used by individuals with short, long, or irregular cycles, but it is time consuming to teach, learn, and practice. Based on the rules of the cervical mucus or ovulation method, the user avoids unprotected intercourse for approximately 14 to 17 days each cycle. (See 'Cervical mucus or ovulation method' above.)

•Symptothermal method – The symptothermal method requires individuals to observe and evaluate their cervical secretions several times each day and take their temperature with a BBT thermometer each morning before rising. This method can be used by those with short, long, or irregular cycles. Users of the symptothermal method avoid unprotected intercourse for approximately 12 to 17 days each cycle. (See 'Symptothermal method' above.)