Early Day Rules for Pregnancy Avoidance
For pregnancy avoidance the BOM has four rules, three Early Day
Rules and the Peak rule. The Early Day Rules are formulated to give
the earliest possible prediction of ovulation to allow for the longest
possible sperm survivals. As the BOM relies on sensation at the
vulva, and time is required for the discharges to drain into the
vulval area, time by the woman in the upright position is required
for accurate identification. Furthermore, seminal fluid obscures
the observations and needs to be absorbed or drained away before
accurate observations can be made. Therefore, to achieve these two
requirements for all the types of ovarian activity the Early Day
Rules state the following:
- Times of the full menstrual flow or other types of bleeding
are not available for intercourse since these obscure the discharge
symptoms . Intercourse may be resumed towards the end of menstrual
bleeding (that is bleeding following a distinct PC and Peak day)
when it is light or spotting is occurring, provided that the fertility
symptoms are not being obscured.
- When a BIP is identified, alternate evenings are available for
intercourse.
- When a change from a BIP discharge or bleeding is observed the
couple waits without intercourse. If the same BIP returns, intercourse
may be resumed on the fourth evening after the return of the BIP.
This is the wait and see, one, two, three rule.
More usually, the change from a BIP is progressive with the discharge
changing daily in characteristics which are becoming increasingly
fertile, slipperiness being the most important final quality. The
phase of possible fertility begins with the first change from the
BIP (the ER) and from then on a time of no genital contact is observed.
In short cycles, there may be insufficient time after bleeding to
identify a BIP before a follicle begins to develop, in which case
no pre-ovulatory days are available for intercourse. Occasionally
during breast-feeding or approach of menopause, a BIP may change
to another BIP with more fertile characteristics. In this case a
wait-and-see period of 2 weeks is required before assuming that
the change is in fact to a new BIP before resuming intercourse.
The woman notes that the change is not progressive ("not going
anywhere"). When no PC providing recognition of the Peak day
is observed, the woman continues to apply the Early Day Rules.
The Peak Rule for Pregnancy Avoidance
The Peak day is the last day that mucus with fertile characteristics
(slippery) is felt before the progesterone change (PC). It is thus
determined retrospectively by this change. The Peak rule states
that intercourse may be resumed on the fourth morning after the
Peak day. All times from then until the next menstruation are available
for intercourse. The Peak rule provides a well-tested minimum safety
margin between the resumption of intercourse at the beginning of
the post-ovulatory infertile phase and the Peak day, which is the
day of maximum fertility.
Pregnancy Achievement
For pregnancy achievement, the couple aims to have intercourse
on the Peak day, the day of peak fertility. However, the Peak day
is identified in retrospect by the progesterone change, and, furthermore,
intercourse on the Peak day produces seminal fluid which obscures
this change. Therefore, in these circumstances, the Peak day cannot
be determined with certainty. The best that can be done is to have
intercourse when the discharges seem to be maximally fertile, namely
when a slippery sensation is felt at the vulva. This is understood
more clearly by those women who have had previous experience with
their symptoms in avoiding pregnancy. When the timing is correct
and no pregnancy results, the couple usually begin to despair and
want to know the reason. Fertility is one of the most variable phenomena
in human activity and is the sum total of both partners' fertility.
The most fertile couples are those where the man produces the most
robust and numerous sperm and the woman provides the longest and
best cervical mucus production to nurture them. Such couples conceive
following almost any act of intercourse during the fertile phase
with a pregnancy rate of about 70% per act of intercourse during
the fertile phase. At the other end of the spectrum, the combined
sperm/mucus interaction of the couple may be so poor that the sperm
have fertilizing ability only for the few hours of optimum mucus
production close to ovulation. These couples are self selecting
and are the main group presenting with infertility. They have a
probability of conception of about 10% per cycle and therefore,
without accurate timing of intercourse, it would take several years
of trying before the majority had achieved pregnancy. When conception
has not occurred within say six successfully timed cycles using
the BOM symptoms, it is worth trying even more accurate methods
of timing ovulation such as the LH kits or the Home Ovarian Monitor.
Failing to conceive when wanted is stressful and therefore favours
infertility. It should be remembered that, apart from a few conditions
such as blocked fallopian tubes, absent sperm and continued anovulation,
most couples will conceive eventually without help. However, the
modern expectation is one of immediate results and the main function
of assisted reproduction techniques is therefore to shorten the
waiting time for conception.
It is seen that the rules of the BOM cope effectively with all
the types of ovarian activity yet discovered. It should be emphasized
that the BOM recognizes only one type of cycle, that is the ovulatory
cycle in which a PC providing calculation of a Peak day is observed
and which therefore ends with menstruation. This includes the fully
fertile ovulatory cycle and the infertile ovulatory cycles with
deficient or short luteal phases. The first day of menstruation
is counted as the first day of the cycle. Bleeding which occurs
without a Peak day preceding it is not counted as the end of a cycle
but is considered to be still the early part of an ovulatory (possibly
fertile) cycle which will follow it. Thus the emphasis in the BOM
is on cyclic fertility. This contrasts with other definitions which
refer to cycles of bleeding or cycles of ovarian activity. Thus
it is possible to have ovulatory or anovulatory cycles of bleeding
or of ovarian activity. In our work in measuring hormone production
the term "cycle" has been applied to the growth and regression
of follicles within the ovaries whether they ovulate or not by measuring
the rise and fall in oestrogen and progesterone production. Thus
this application of the term "cycle" refers to cyclic
ovarian activity which is related to but not identical with cyclic
fertility. The distinction is made by the BOM to steer women away
from the old concept of concentrating on the bleeding symptom, which
is uninformative, and making them concentrate on the fertility symptoms
which are really what matter. Furthermore, the BOM concentrates
on the patterns of discharges which reflect the underlying dynamic
ovarian events associated with fertility and infertility rather
than on the detailed descriptions of the discharges which vary from
woman to woman.
Research Effort
The BOM was developed only after a complete appraisal of the NFP
methods which were available in the late 1950s, including the rhythm
method and the use of the BBT, and finding that none could hope
to match the newly developed contraceptive pill in efficacy and
acceptability. The above understanding of the application of the
vaginal discharge symptoms to fertility awareness, as applied in
the BOM, has been arrived at after more than 30 years of intensive
research which has had little support from granting bodies. Firstly,
the observations were made on the women themselves as the rules
were developed and used in practice. Some women planning pregnancy
volunteered to test their fertility on days relative to the Peak
day and all pregnancies were carefully assessed as to the timing
of the intercourse which caused them. Secondly, Professor Erik Odeblad,
in Sweden, has done years of pioneering work on typing the cervical
mucus and determining the significance of each type in the fertility
process. Thirdly, the above study of the relationship between the
mucus changes, ovarian activity and fertility involved approximately
750,000 hormone assays for both pregnancy avoidance and achievement,
countless ultrasound observations and the monitored use of FSH,
LH (HCG) and clomiphene in the induction of ovulation. Such a large
study has been necessary because approximately 90% of ovarian cycles
are ovulatory and the remaining 10% are distributed among the other
variants. The ovulatory cycle has been extensively studied by many
workers but the other variants have been largely overlooked. This
is because these other variants are not predictable and large numbers
of cycles needed to be studied so that the variants could be documented
and their mechanism, frequency and impact on the mucus symptoms
and fertility determined. To expedite the study, the search was
concentrated on those times when these cycle variants are most common,
namely menarche, stress, infertility, postpartum, breast-feeding
and approach of menopause. Because NFP operates with an intact and
functioning reproductive system, it has been important to study
all the types of ovarian activity that occur in women so that the
times of possible fertility and absolute infertility can be recognized
with certainty and the full potential of the method can be realized.
The work involved in the overall development of modem methods of
NFP has necessarily been far more extensive and demanding than that
required for other methods of family planning, all of which are
designed to interfere predictably in the intricate processes of
reproduction and the main research requirement has been to determine
efficacy, acceptability and the minimization of deleterious side
effects. It should be stated that much of this research in NFP has
been conducted in parallel with research in assisted reproduction
and that each field has made important contributions to the other.
In fact, it is unlikely that the full potential of either field
is possible without the information provided by the other. This
is the direction of further research.
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