‘Fertility Awareness-Based Methods’ and subfertility: a systema­tic review

Abstract

Fertility awareness based methods (FABMs) can be used to ameliorate the likelihood to conceive. A literature search was performed to evaluate the relationship of cervical mucus monitoring (CMM) and the day-specific pregnancy rate, in case of subfertility. A MEDLINE search revealed a total of 3331 articles. After excluding articles based on their relevance, 10 studies and were selected. The observed studies demonstrated that the cervical mucus monitoring (CMM) can identify the days with the highest pregnancy rate. According to the literature, the quality
of the vaginal discharge correlates well with the cycle-specific probability of pregnancy in normally fertile couples but less in subfertile couples. The results indicate an urgent need for more prospective randomised trials and prospective cohort studies on CMM in a subfertile population to evaluate the effectiveness of CMM in the subfertile couple.

Full text

113
Introduction
Only 2% of nally successful couples conceived
after 12 cycles with unprotected intercourse. After
six unsuccessful cycles, subfertility has to be
assumed in 50% of all couples (Gnoth et al., 2003;
Wang et al., 2003; Sozou and Hartshorne, 2012).
Besides surgical and medical treatment for those
couples, there is a tremendous uprising trend to use-
assisted reproductive technologies (ART). ART
comprises all treatments or procedures used to
establish a pregnancy in which there is in vitro
handling of human oocytes, sperm and/or embryo.
The development of these techniques surely has led
to overtreatment in fertility care. However, there are
other less-known measures to ameliorate the likeli-
hood to conceive, the so-called fertility awareness-
based methods (FABMs).
FABMs use physical signs and symptoms that
change along with hormone uctuations throughout
the different phases of a woman’s menstrual cycle
to predict and monitor the fertile and infertile days
(Pallone and Bergus, 2009). This knowledge, re-
ferred to as ‘fertility awareness’, can be used either
to plan or to avoid a pregnancy. The key variables
which FABMs rely on are the reliable identication
of the fertile window (FW) and modication of
sexual behaviour (Frank-Herrmann et al., 2007).
Different modications of FABMs are known, cer-
vical mucus based methods, temperature methods,
combinations of both variables and calculation
methods. The most extensively studied method is
Sensiplan®, the symptothermal method of Natural
Family Planning (NFP), mucus, temperature and
calculation rules (Frank-Herrmann et al., 2007).
There is a compelling need to educate women
about their fertility awareness. Primary care
providers need to integrate fertility health literacy
into health promotion of women of reproductive
age. The guideline currently recommended by many
physicians is that women who wish to become
pregnant should have frequent random intercourse,
‘Fertility Awareness-Based Methods’ and subfertility:
a systema tic review
A. Thijssen1,2, A. Meier2, K. PAnis2, W. OMbeleT1,2
1Genk Institute for Fertility Technology, Department of Obstetrics and Gynaecology, Ziekenhuis Oost-Limburg, Schiepse
Bos 6, 3600 Genk, Belgium.
2Faculty of Medicine and Life Sciences, Hasselt University, Martelarenlaan 42, 3500 Hasselt, Belgium.
Correspondence at: annelies.thijssen@uhasselt.be
FAcTs VieWs Vis Obgyn, 2014, 6 (3): 113-123 Structured review
Abstract
Fertility awareness based methods (FABMs) can be used to ameliorate the likelihood to conceive. A literature
search was performed to evaluate the relationship of cervical mucus monitoring (CMM) and the day-specific
pregnancy rate, in case of subfertility. A MEDLINE search revealed a total of 3331 articles. After excluding articles
based on their relevance, 10 studies and were selected. The observed studies demonstrated that the cervical mucus
monitoring (CMM) can identify the days with the highest pregnancy rate. According to the literature, the quality
of the vaginal discharge correlates well with the cycle-specific probability of pregnancy in normally fertile couples
but less in subfertile couples. The results indicate an urgent need for more prospective randomised trials and
prospective cohort studies on CMM in a subfertile population to evaluate the effectiveness of CMM in the subfertile
couple.
Keywords: Billings method, cervical mucus, conception, Creighton model, fertility awareness, infertility, natural
family planning, subfertility, symptothermal method.

114 FAcTs VieWs Vis Obgyn
ovarian function in women has been exact ovulation
detection through the use of daily sonography and
specic hormone testing (estradiol, luteinizing
hormone, progesterone) (Albertson and Zinaman,
1987). These clinical methods for cycle monitoring
are expensive and time-consuming. FABMs show
the same reliable results for determining the FW
and predicting the time of ovulation. The methods
are based on a detection of the FW and use symp-
toms the women are able to observe themselves,
such as bleeding rhythm, cervical mucus, measure-
ment of the basal body temperature, auto-palpation
of the cervix, etc. (Gnoth et al., 1996; Frank-
Herrmann et al., 2005). The rhythm method or
calendar-based method requires to calculate the
fertile days according to the length of the menstrual
cycles. This is possible because the duration of the
luteal phase is relatively stable (Evans-Hoeker et
al., 2013). The basal body temperature (BBT)
method uses a temperature elevation to determine
the day of ovulation. This rise (0.3° to 0.6° C) is due
to the progesterone surge (Pallone and Bergus,
2009). After ovulation, the BBT remains elevated
due to increased progesterone levels after ovulation
until next menstruation. Therefore, the temperature
rise identies the end, rather than the onset of the
fertile period. This implies that this method can
only be used to retrospectively identify ovulation.
Furthermore, there are other factors that limit the
accuracy of a BBT method used solely. Temperature
measurements may be disturbed by a variety of
factors, some women ovulate without a clear rise in
BBT and the shift may vary up to one day before
and three days after actual ovulation (Pallone and
Bergus, 2009).
On the other hand, cervical mucus patterns, which
reect rising estradiol, are shown to be accurate
markers of the onset of the fertile and infertile
phases of a woman’s menstrual cycle (Hume, 1991).
Cervical mucus is an aqueous or gel mixture of
proteins and mucopolysaccharids, ions and
compounds, and cells, primarily produced by the
endocervical epithelium (Fordney-Settlage, 1981).
Estradiol and progesterone levels are responsible
for the changes in characteristics of cervical
secretions during the menstrual cycle. Mucus
characteristics have been tried to be typed. The
secretion of the oestrogenic mucus (E mucus) is
stimulated by the rise in oestrogen produced by the
dominant follicle ve to six days before ovulation.
E mucus is clear, wet, stretchy and slippery, which
makes it ideal to facilitate the transport and the
survival of the spermatozoa in the cervix. In
addition, it leads to functional maturation of sperm
(capacitation) so that the fertilisation potential of
the ovum is increased. This mucus is present in the
optimally every other day. With application of this
guideline, some acts of intercourse will occur in the
FW (ASRM, 2008).
The use of FABMs could increase the pregnancy
rate when used properly. Our systematic review will
focus on cervical mucus and its function to become
a useful FABM. Previous studies showed that more
oestrogen-type mucus is present in the fertile days
of the menstrual cycle, but also an increasing trend
in the amount of mucus secretions can be noticed.
This rise in volume is associated with a change in
vaginal discharge, which women can monitor based
on different characteristics (Hilgers and Prebil,
1979). In addition, this awareness can be used to
evaluate the ovarian function (Moghissi et al.,
1972). It also provides information about the fertility
status of the different days in the cycle, because
fertile type mucus ensures a facilitated transport of
sperm cells to the ovary through the fallopian tubes
(Billings et al., 1972; Katz et al., 1997).
The main objective of this review was to
determine the effectiveness of cervical mucus as a
predictor for the FW. Furthermore, the probability
of whether or not cervical mucus monitoring is
associated with increased cycle-specic pregnancy
rates will be specically examined for the subfertile
couple.
Different methods for fertility awareness assessment
All FABMs are based on the detection of ovulation
and the related fertile window. Retrospectively,
ovulation occurred approximately 14 days before
the onset of the next menstrual cycle (Wilcox et al.,
2000). Throughout the woman’s menstrual cycle,
there is a six day fertile interval during which
conception more likely occurs if intercourse takes
place (Bilian et al., 2010). This FW comprises the
ve days before ovulation and the day of ovulation
itself. There is only a limited period of time during
which fertilisation can take place due to the limited
duration of viability of the ovum and sperm which
accounts for the different probabilities of conception
for days of the menstrual cycle (Colombo and
Masarotto, 2000). After ovulation has occurred, the
ovum will lose its ability to become fertilised after
10 to 24 hours (Stanford et al., 2002). The life span
of sperm within the female reproductive tract is
more variable. Spermatozoa have a life span of 24-
48 hours if hostile mucus is absent. When there is
proper oestrogenic cervical mucus, the fertilising
capacity of sperm can last 3-7 days in the perio-
vulatory period (Pallone and Bergus, 2009).
There has been a search for simple and reliable
methods for both predicting and conrming
ovulation. The golden standard of monitoring

FerTiliTy AWAreness-bAseD MeThODs – Thijssen eT Al. 115
mucus secretions of dry/humid feeling. In some
elaborated mucus methods women are asked to
describe the colour, texture and stretch of the
cervical discharge (Pallone and Bergus, 2009).
Table I shows four mucus categories ranging from
absence of discharge or dry mucus characteristics
(score 1) to transparent, stretchy and slippery mucus
(score 4) which is the commonly used typing. A
high mucus score is consistent with the presence of
fertile-type E mucus. Important conception studies
are based on this typology of mucus (Colombo and
Masarotto, 2000; Dunson et al., 2001; Bigelow et
al., 2004).
The rst method described is the Billings Ovula-
tion Method (BOM), in which women record the
mucus secretions ‘in their own words’ with a focus
on changes in cervical characteristics (Bhargava et
al., 1996; Stanford et al., 1999). Another more
standardised method, named the Creighton Model
(CrM), characterises cervical secretions by pictures
and precise words (Howard and Stanford, 1999;
Pallone and Bergus, 2009). In addition to the
methods above, the TwoDays Method (TDM) is the
simplest method, which focuses on the presence
or absence of cervical mucus and not on the
fertile phase of the menstruation cycle. Following
ovulation there is a second type of mucus, the
progesterone mucus (G mucus). This type is
produced by the progesterone release from the
corpus luteum. Progesterone stimulates the cervix
to produce G mucus, which inhibits sperm capacita-
tion and motility and blocks the passage of sperm.
This cervical secretion is considered infertile due to
the unchanging and generally dry, sticky, cloudy
and not stretching characteristics (Pallone and
Bergus, 2009; Stanford et al., 2002).
Cervical mucus monitoring (CMM) is performed
by observing these mucus secretions, whereby
internal checking of the vagina or cervix is not
necessary (Evans-Hoeker et al., 2013). The goal is
to identify the onset of the production of any type of
fertile mucus. Even a change of feeling (dry to
humid or wet) may be indicative of impending
fertility. The peak day can be identied as the last
day of any vaginal discharge that has type E charac-
teristics (Fig. 1) (Stanford et al., 2002). There are
different methods that use cervical mucus as a pre-
dictor of the FW. Each method uses a different way
to identify the fertile phase, but the main focus relies
on observing the absence or presence of cervical
Fig. 1. — Physiologic parameters of the menstrual cycle that can be used to identify days during which intercourse may result in
pregnancy, i.e. the fertile window. LH: luteinizing hormone; P: peak day (Adapted from Stanford et al., 2002).

116 FAcTs VieWs Vis Obgyn
readers regarding the relevance of the title, resulting
in 315 remaining articles. After reading the abstracts
in the following stage, 39 articles were retained.
Having read the 39 papers carefully, the following
articles were excluded: studies mainly focusing on
avoiding pregnancy or natural family planning used
for contraceptive procedures and articles with
reference to cancer, breastfeeding or sex pre-
selection. Studies where cervical mucus was used
for the determination of the FW were included.
These also comprise methods like the Creighton
Model, the Billings Ovulation Method, the TwoDays
Method and the Symptothermal Method. Ultimately,
10 relevant studies were selected. Examining the
reference lists of the selected articles yielded no
new hits. A schematic overview of the search
strategy can be seen in Figure 2.
Results
Multiple studies have been performed to obtain
information about the day-specic probability of
conception through observation of the vaginal
discharge, used as a marker of ovulation. This
systematic review compares the results of ten
different studies and examines the relevance and
outcome of each study. Nine out of the ten selected
articles were prospective cohort studies and one was
a retrospective cohort study (Table V).
Stanford et al. (2003) retrospectively evaluated-
data extracted from the Creighton Model Fertility
Care System in four different cities. Fertile and sub-
fertile couples were identied and, after selection,
1681 cycles from 309 fertile couples resulting in
80 pregnancies and 373 cycles from 117 subfertile
couples which resulted in 30 pregnancies, were
incorporated in the study. The highest probability of
conception could be seen on the mucus peak day
(identied as ovulation), both for fertile and
subfertile couples. For the fertile couples, the
probability to become pregnant on the mucus peak
day was 0,38 and for the subfertile couples 0,14.
The mucus peak day was appointed day 0. The
characteristics of the secretions (Dunson et al.,
2001). A woman is considered fertile on a given day
if she notices secretions on that specic day or the
previous day (Jennings et al., 2011).
The Symptothermal Method (Sensiplan®) uses a
combination of predictors, namely the BBT, record-
ing of cervical secretions and, important, calcula-
tion rules (Frank-Herrmann et al., 2007; Pallone
and Bergus, 2009). The opening of the FW is calcu-
lated from previous cycles (min. 12) but detection
of any fertile type of mucus marks the abrupt onset
of impending fertility (“what comes rst”). The
change of cervical mucus together with the rise in
BBT indicates the end of the fertile phase (“what
comes last”). Therefore, this method can be used
prospectively as well as retrospectively to identify
the periovulatory period (Gross, 1987). This meth-
od has been proven to be very effective in prospec-
tive studies (Frank-Herrmann et al., 2007) because
it is based on a double check mechanism: It can be
used by women with short, long or irregular cycles
(Frank-Herrmann et al., 2007) (Pallone and Bergus,
2009). Table II provides a short overview of the
different FABMs.
Materials and Methods
Search strategy
We made use of a computerised literature search
executed to search for studies examining the value
of CMM, specically applied to the subfertile
couple. The database used was MEDLINE, and the
following search terms were considered: fertility
awareness, self-assessment, cervical mucus,
infertility, subfertility, natural family planning,
conception, Symptothermal Method, Billings
Ovulation Method, Creighton Model, in combination
with ‘not contraception’. These keywords were
used in different combinations which led to 3331
hits. No time limitation or other lters such as
language restriction were entered in the search.
Subsequently, the reports were screened by two
Table I. — Classication of mucus symptoms from vaginal discharge.
Mucus score Feeling Appearance Secretions
1Dry, rough and itchy
or nothing felt
Nothing seen No secretions
2Damp Nothing seen Secretions
3Damp Mucus is thick, creamy, whitish, yellowish, or
sticky
Secretions
4Wet, slippery, smooth Mucus is transparent, like raw egg white, stretchy/
elastic , liquid, watery, or reddish
Secretions
(Adapted from Colombo and Masarotto (2000)).

FerTiliTy AWAreness-bAseD MeThODs – Thijssen eT Al. 117
showed that although ovulation detection can be
adequately determined with the peak mucus
symptom and the BBT, the combination gave a
signicant better correlation for a correct
identication of ovulation. Furthermore, the study
investigated the role of the changing quality of the
cervical mucus in relation to the probability of
conception. This technique was used by 346 women
and resulted in a cumulative probability of
probability of conception was greater than 0,5 for
day -3 to day +2 for the fertile couples and for day
-1 to day +1 for the subfertile couples.
Frank-Herrmann et al. (2005) reviewed the main
results of recent European cycle databases (WHO
database, German Long-term Cycle database, I
European Cycle Database and II European Cycle
Database) on ovulation detection and determination
of the FW performed by women themselves. Results
Fig. 2. — Schematic overview of the search strategy
Table II. — Overview of the different FABMs.
Methods Mechanism
Rhythm (calendar-based) method Calculation of the fertile days according to the length of a woman’s
previous menstrual cycles
The basal body temperature method Charting the BBT to detect ovulation day
Billings ovulation method Identication of the changes in vaginal discharge in a woman’s own
words
Creighton Model Identication of the changes in vaginal discharge with use of
pictures and suggested words
TwoDays Method Focus on the presence or absence of cervical mucus
Symptothermal Method Identication of the FW through use of the BBT and cervical
secretions

118 FAcTs VieWs Vis Obgyn
days before ovulation and ending on the estimated
ovulation day, with the peak day being two days
prior to the estimated ovulation. Additionally, the
pregnancy rate increased by 50% when women had
cervical mucus secretions for two days.
Also Bigelow et al. (2004) made use of the ESDF
database. From the database, 1473 cycles remained
after exclusion, resulting in 353 pregnancies. The
aim was to determine the day-specic probabilities
of pregnancy according to the timing of intercourse
relative to ovulation and/or the mucus characteristics.
The outcome proved that the day of lowest fertility
is ve days before ovulation and the day of highest
fertility is three days before ovulation, as detected
by BBT. However, the differences in daily-
fecundability are more attributable to a rise in
mucus score than the timing of intercourse relative
to ovulation.
The next three prospective multicentre studies
(Colombo et al., 2006; Scarpa et al., 2006; Scarpa et
al., 2007) used another database which included
193 couples from four Italian centres using the
Billings Ovulation method. Inclusion criteria and
mucus scoring were similar to the ESDF study
(Table III and Table I respectively).
The rst study was performed by Colombo et al.
(2006) aiming to determine the effect of cervical
mucus symptoms on the daily fecundability. The
earlier study performed by Colombo and Masarotto
in 2000, had the objective to determine the relation-
ship between the intercourse patterns and the
fecundability (Table IV). In 2000, outcome
measures included 3255 cycles, 435 of which
resulted in a pregnancy; in 2006 respectively
963 cycles and 142 pregnancies (Colombo and
Masarotto, 2000; Colombo et al., 2006).
The mucus reference day, identied as day 0, is
dened as being the last day with the best quality or
peak mucus in a specic cycle, with uid mucus
and/or a wet-slippery sensation. Results showed
that the highest pregnancy rate can be found on day
0 with a probability of 0,429 in 2006, respectively
on day -2 with a probability of 0,203 in 2000.
conception of 81% after 6 months and 92% after
12 months.
Evans-Hoeker et al. (2013), investigated the use
and consistency of cervical mucus monitoring
(CMM) to determine the FW in women who wanted
to get pregnant. The second goal was to examine
whether monitoring mucus was associated with an
increased cycle-specic probability of conception
independent of intercourse frequency or use of
urinary luteinizing hormone monitoring kits. This
time-to-pregnancy study examined a cohort of 331
women between 30 and 44 years of age who had
been trying to conceive for three months or less and
had no known issues related to fertility. If women
checked their cervical mucus on a particular day,
they had to make a choice which type they observed
(Table I).The FW could be estimated through the
use of calendar based calculations. Cycles in which
women made consistent use of CMM were more
likely to result in conception. The results of this
study showed that fecundability increased with
increasing use of CMM.
A large multinational prospective cohort study,
the European Study of Daily Fecundability (ESDF,
database: Fertili), was conducted by Colombo and
Masarotto (2000) to determine the daily probability
of conception (Table IV) among healthy women
and to compare different statistical models on the
matter. Inclusion criteria for the ESDF are listed in
Table III. Women were instructed to keep daily
records of their BBT, cervical mucus symptoms
(Table I) and coitus. The results found by Colombo
and Masarotto (2000) are described in the next
section together with their results of a more recent
study (Colombo et al., 2006).
Dunson et al. (2001) used the data from the ESDF
to evaluate the theoretical effectiveness of the Two-
Day Algorithm. Out of the 2832 cycles studied, 434
resulted in a pregnancy. Data suggested that, for
most women, the TwoDay Algorithm was useful in
identifying the most fertile days of the menstrual
cycle. They showed that the pregnancy probability
was highest in the six day interval, beginning ve
Table III. — Overview of the inclusion criteria for the ESDF.
Women are experienced in use of a Natural Family Planning method
Married or in a stable relationship
Age: 18-40
Having at least one menses after cessation of breastfeeding or after delivery
No use of drugs or hormonal medications that could affect fertility
Couples have no history of fertility problems or disorders that might cause subfertility
Not mixing unprotected and protected intercourse

FerTiliTy AWAreness-bAseD MeThODs – Thijssen eT Al. 119
pregnancy rates when women were having
intercourse during the FW in which there was a
differentiation between self-estimated high, peak
and low fertile days. Figure 3 shows a cycle with
correct use of intercourse patterns on high and peak
fertility rated days, which resulted in a pregnancy.
A 12-month prospective, observational cohort
design was used to study 124 women seeking to
become pregnant with the use of this natural family
planning method. To determine their fertile days the
women utilised either cervical mucus monitoring or
electronic hormonal fertility monitoring (EHFM) or
both. The analysis showed a pregnancy rate of 0,87
at 12 months of trying when intercourse happened
on either high or peak days during the fertile window
and a pregnancy rate of 0,5 when intercourse
occurred only on days with a low mucus score.
Discussion
Fertility awareness based methods (FABMs) are
another measure a couple can take to ameliorate
their likelihood to conceive. In order to evaluate the
effectiveness of cervical mucus monitoring (CMM)
in shortening the time to pregnancy, especially for
the subfertile couple, a literature search was
performed. After selection, a total of 10 articles
remained to be included in this systematic review.
The highest probability of conception is one or
two days before ovulation (Dunson et al., 1999;
Colombo and Masarotto, 2000; Dunson et al., 2001)
calculated from models solely using BBT signals.
The second study (Scarpa et al., 2006) investigated
the relationship between the self-observed
characteristics of cervical mucus on the day of
intercourse and the day-specic probability of
conception across the menstrual cycle. The most
fertile type mucus (mucus score 4) was registered
for six days on average. In general, mucus score 4
had a peak on day 13 of the cycle, in contradiction
to mucus score 1 which was unlikely to be seen
midcycle. Moreover, results showed that the
conception probabilities varied among the mucus
scores, increasing from mucus score 1 with a
probability of 0,003 to a mucus score 4 with a
probability of 0,29. In between, there was a
conception probability of 0,013 for days with mucus
score 2 and 0,025 for days with mucus score 3.
The third study (Scarpa et al., 2007) determined
adequate rules for timing of coitus to achieve
conception, based on calendar and cervical mucus.
Results showed that, in a midcycle interval begin-
ning on day 7 and ending on day 20, the probability
of conception increased with a rise in mucus score.
On days with the highest mucus score, there was a
40 times higher conception probability than on days
when no mucus score was noticed. Outside this
midcycle interval, conception probabilities were
negligible. Rules were established, based on the
increase in frequency of coitus on days within a
midcycle interval which had a mucus score at or
above a threshold value on a scale from 1 to 4.
The purpose of the nal examined study (Mu and
Fehring, 2014) was to determine and compare
Fig. 3. — Pregnancy cycle with correct use intercourse pattern on high and peakfertility rated days. (Adapted from Mu
and Fehring (2014)).
Table IV. — Daily probabilities of conception referenced to the day of temperature rise (3175 natural cycles with 434
pregnancies) according to (Colombo and Masarotto, 2000).
- 8 - 7 - 6 - 5 - 4 - 3 - 2 - 1 Temp.rise +1 +2
0,3% 1,4% 2,7% 6,8% 17,6% 23,7% 25,5% 21,2% 10,3% 0,8% 0,35%

120 FAcTs VieWs Vis Obgyn
Another important issue is the relevance of coital
patterns. The ASRM recommends sexual intercourse
at least every other day to optimize natural fertility
(ASRM, 2008). However, in case of subfertility,
there is no place to recommend just an increase of
coital frequency probably causing an increase of
psychological stress only. In contrary, couples
should be informed about the fact that a single
episode of intercourse on a day of highly fertile
mucus gives nearly the same chance of pregnancy
then multiple acts (Bilian et al., 2010).
Until now, most studies used a small sample size
and there is a need for prospective studies including
couples planning to become pregnant. Most studies
examined either excluded couples with fertility
problems or did not take them into account. We
urgently need a prospective study comparing fertile
and subfertile groups of couples with a duration of
infertility for at least 6 months and without an
obvious reason for infertility, such as tubal factor or
a very poor sperm quality.
Our ndings indicate that natural family planning
methods can be used as a diagnostic tool to identify
subfertility and its possible causes, but also provide
a better understanding of the menstrual cycle (Gnoth
et al., 2003). However, we still lack research on-
subfertile couples who use CMM and evaluate the
effect on conception probability and time to
pregnancy.
Most studies that rely on mucus observations are
classied according to a rough 1 to 4 scale. This
scheme is non-invasive and easy to implement after
a minimal amount of training. It could be interesting
to better quantify these mucus characteristics and to
remove the potential subjectivity in this
classication. A few studies (Scarpa et al., 2006;
Evans-Hoeker et al., 2013) suggested to assess the
utility of urinary LH monitoring with CMM for
couples attempting pregnancy. A randomised trial
could provide information on the precise
relationships that exist between hormones and
mucus for women varying in their fecundability.
Until now, there are no evidence-based guide-
lines for couples to shorten their time to pregnancy
by timing intercourse. The only recommendation,
not evidence-based, is to have frequent intercourse
every other day. It is important for women to know
that CMM can decrease the time to pregnancy if
used properly. This method is easily taught with the
help of nurses/physicians and online education
(Sensiplan®). The combination of these two sources
of education and the use of an online fertility
charting system, can provide an efcient system to
shorten the time to pregnancy in a selected group of
patients with no obvious cause for infertility (Mu
and Fehring, 2014). However, evidence showed that
But for clinical usage the mucus symptom is
superior. Dunson et al. (2001) identied the
relationship between cervical secretions and day-
specic fecundability, providing evidence that
cervical mucus monitoring can be offered to couples
who are trying to conceive. By timing intercourse
on days with noticeable secretions, couples can
signicantly increase their chance of achieving
pregnancy (Bigelow et al., 2004) and Stanford et al.
(2003) showed that the highest pregnancy rate can
be seen on the mucus peak day (identied as
ovulation) both for fertile and subfertile couples.
Furthermore, the quality of the vaginal discharge
correlates well with the cycle-specic probability of
pregnancy in normally fertile couples but not in
subfertile couples (Stanford et al., 2003; Frank-
Herrmann et al., 2005; Scarpa et al., 2006). However,
several weaknesses of the study by Stanford et al.
(2003) should be taken into account: (i) there was
no independent marker of ovulation and (ii) the
retrospective design of the study.
Scarpa et al. (2006) compared their results with a
study performed by Wilcox et al. (2001). The
probability of conception on the peak day described
by Wilcox et al. (2001) is substantially lower than
the ndings reported by Scarpa et al. (2006). This
difference might be explained because, in the
Wilcox study, couples who wished to conceive were
less fertile than the couples selected for the Scarpa
study, who had more regular menstrual cycles. The
difference in fecundability on the peak mucus day
may be caused by including women who had already
given birth, which yielded a higher probability to
become pregnant. Despite this difference in the
probability of conception on the peak day by Scarpa
et al. (2006) and Wilcox et al. (2001), the number of
days with the most fertile-type mucus symptom was
six days in both studies.The pattern of the
occurrences of the different types of mucus
throughout the cycle and the peak day on day 13,
corresponds with previously described outcomes
(Wilcox et al., 2000).
To efciently shorten the time to pregnancy, a
couple could rely on timing coitus during self-
estimated high and peak fertile days in the FW,
based on days with the most fertile-type mucus
symptom (Scarpa et al., 2007; Evans-Hoeker et al.,
2013; Mu and Fehring, 2014). Scarpa et al. (2007)
suggested rules for timing intercourse to have a
higher probability of conception. However, among
women, there are differences in age, hormone
secretions, length of the menstrual cycles and
numbers of cycles attempting. This indicates that
some recommendationsmight work for some
couples, but not for everyone due to woman-specic
characteristics.

FerTiliTy AWAreness-bAseD MeThODs – Thijssen eT Al. 121
Ta
bl
e V. — Summa
r
isa
t
ionof
t
he
e
xamined s
t
udi
e
s.
Author Year Country Study design Population N° of
couples
N° of
cycles
N° of
pregnancys
Colombo, et al.
2000 Europe Prospective Fertile NA 3265 434
Highest probability of conception is two days before the peak mucus day.
Dunson, et al.
2001 Europe Prospective Fertile 660 2832 434
The days estimated by the TwoDay Algorithm as fertile were the days with the
highest fecundability. There is twice as much chance to achieve a pregnancy
when intercourse nds place on a day covered by the TwoDay
Algorithm.
Stanford, et al.
2003 USA Retrospective Fertile 309 1681 81 Observation of the vaginal mucus discharge can identify the days with the
highest pregnancy rate from intercourse in normal fertility and subfertility.
Subfertile 117 373 30
There is a signicant effect of the quality of mucus discharge on the cycle
- -
specic probability on conception by fertile couples, this relationship
couldn’t be found the subfertile couple.
Bigelow, et al.
2004 Europe Prospective Fertile NA 1473 353 Increasing trend in the day
- -
specic probabilities of pregnancy with increases
in the mucus score.
Frank
- -
Herrmann,
et al.
2005 Germany Prospective Fertile NA 62 NA Cervical mucus symptoms in combination with BBT have a good
correlation with ovulation.
346 NA NA Women can monitor their cervical mucus changes to increase their
probability of pregnancy. FABMs seem to shorten the time to pregnancy,
and can be used in the management of subfertility.
Colombo, et al.
2006 Italy Prospective Fertile NA 963 142 Highest probability of conception: peak mucus day (day 0). A relationship
between the presence of the mucus symptom and the pregnancy rate could
be established.
Scarpa, et al.
2006 Italy Prospective Fertile 191 2536 161 Conception probability is negligible on days with no noticeable mucus
secretions and approximately 30% for days with most fertile
- -
type mucus
detected by woman.
Scarpa, et al.
2007 Italy Prospective Fertile 191 2536 161 TTP can be shortened when intercourse takes place on days with the
highest
mucus
score.
Evans
--
Hoeker,
et al.
2013 USA Prospective Fertile 331 NA NA Fecundability increases with increasing consistency of CMM. The time to
pregnancy can be reduced through use of CMM.
Mu, et al.
2014 USA Prospective Fertile 124 469 NA
Intercourse on high or peak days increases the pregnancy probability.
BBT
:
basal body
te
mpe
r
a
t
ur
e,
CMM
:
cerv
i
c
al mucus moni
t
oring
,
NA:
not a
v
ailabl
e,
TT
P:
t
im
e
t
o pr
eg
nanc
y
.

122 FAcTs VieWs Vis Obgyn
Bigelow JL, Dunson DB, Stanford JB et al. Mucus observations
in the fertile window: a better predictor of conception than
timing of intercourse. Hum Reprod. 2004;19:889-92.
Bilian X, Heng Z, Shang-chun W et al. Conception probabilities
at different days of menstrual cycle in Chinese women.
Fertil Steril. 2010;94:1208-11.
Billings EL, Brown JB, Billings JJ et al. Symptoms and
hormonal changes accompanying ovulation. Lancet. 1972;1:
282-4.
Colombo B, Masarotto G. Daily fecundability: rst results from
a new data base. Demogr Res. 2000;3:[39] p.
Colombo B, Mion A, Passarin K et al. Cervical mucus symp-
tom and daily fecundability: rst results from a new data-
base. Stat Methods Med Res. 2006;15:161-80.
Dunson DB, Baird DD, Wilcox AJ et al. Day-specic
probabilities of clinical pregnancy based on two studies with
imperfect measures of ovulation. Hum Reprod. 1999;14:
1835-9.
Dunson DB, Sinai I, Colombo B. The relationship between
cervical secretions and the daily probabilities of pregnancy:
effectiveness of the TwoDay Algorithm. Hum Reprod.
2001;16:2278-82.
Evans-Hoeker E, Pritchard DA, Long DL et al. Cervical mucus
monitoring prevalence and associated fecundability in
women trying to conceive. Fertil Steril. 2013;100:1033-8
e1.
Fordney-Settlage D. A review of cervical mucus and sperm
interactions in humans. Int J Fertil. 1981;26:161-9.
Frank-Herrmann P, Gnoth C, Baur S et al. Determination of the
fertile window: reproductive competence of women –
European cycle databases. Gynecol Endocrinol. 2005;20:
305-12.
Frank-Herrmann P, Heil J, Gnoth C 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. Hum Reprod. 2007;
22:1310-9.
Gnoth C, Frank-Herrmann P, Bremme M et al. [How do self-
observed cycle symptoms correlate with ovulation?]. Zen-
tralbl Gynakol. 1996;118:650-4.
Gnoth C, Godehardt D, Godehardt E et al. Time to pregnancy:
results of the German prospective study and impact on the
management of infertility. Hum Reprod. 2003;18:1959-66.
Gnoth C, Maxrath B, Skonieczny T et al. Final ART success
rates: a 10 years survey. Hum Reprod. 2011;26:2239-46.
Gross BA. Natural family planning indicators of ovulation.
Clin Reprod Fertil. 1987;5:91-117.
Hilgers TW, Prebil AM. The ovulation method – vulvar
observations as an index of fertility/infertility. Obstet
Gynecol. 1979;53:12-22.
Howard MP, Stanford JB. Pregnancy probabilities during use
of the Creighton Model Fertility Care System. Arch Fam
Med. 1999;8:391-402.
Hume K. Fertility awareness in the 1990s – the Billings
Ovulation Method of natural family planning, its scientic
basis, practical application and effectiveness. Adv Contra-
cept. 1991;7:301-11.
Jennings V, Sinai I, Sacieta L et al. TwoDay Method: a quick-
start approach. Contraception. 2011;84:144-9.
Katz DF, Slade DA, Nakajima ST. Analysis of pre-ovulatory
changes in cervical mucus hydration and sperm penetrabili-
ty. Adv Contracept. 1997;13:143-51.
Moghissi KS, Syner FN, Evans TN. A composite picture of
the menstrual cycle. Am J Obstet Gynecol. 1972;114:405-
18.
Mu Q, Fehring RJ. Efcacy of achieving pregnancy with fertil-
ity-focused intercourse. MCN Am J Matern Child Nurs.
2014;39:35-40.
Pallone SR, Bergus GR. Fertility awareness-based methods:
another option for family planning. J Am Board Fam Med.
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Scarpa B, Dunson DB, Colombo B. Cervical mucus secretions
most physicians do not give information about this
method and underestimate the value of this approach
(Stanford et al., 1999). All people involved in
infertility care should be informed about the
existence and effectiveness of the FABM, in order
to properly educate women about it and to decrease
the number of couples that will eventually need
assisted reproductive technologies.
Conclusion
Based on the results of the selected studies after
literature search, we can conclude that cervical
mucus secretions can be used as a good predictor of
impending fertility. All evaluated studies
demonstrated that observing the cervical mucus can
identify the days with the highest pregnancy
probability. When intercourse takes place on a day
in the fertile interval with the highest mucus score,
the time to pregnancy can be shortened signicantly.
According to the literature, the quality of the vaginal
discharge correlates well with the cycle-specic
probability of pregnancy in fertile couples but less
in subfertile couples. Most of the results are based
on studies with couples with unknown fertility
status. However, there is some evidence that cervical
mucus monitoring can become a very useful
approach for women with unexplained subfertility.
There is an urgent need for further research to
conrm the effectiveness of the CMM method to
increase the probability of pregnancy in subfertile
couples. If these methods prove to be effective for
the subfertile couple, more patients will become
pregnant without the need of assisted reproductive
technologies (ART). When comparing cumulative
pregnancy rates after ART with cumulative
pregnancy rates in natural cycles (Gnoth et al.,
2011) we nd congruent curves which is beautifully
in line with some simulation models (Stanford et al.,
2010). This suggests that ART may reach natural
fertility rates but cannot exceed them and patients
will not benet from a rush into ART.
These thoughts may help in offering a more
patient-friendly approach within infertility centres
and probably will also reduce ART-related costs for
subfertile couples and social systems.
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