Theory of The Safe Days
The operation of the menstrual cycle is a phenomenon JL with which
scarcely one woman in ten is thoroughly familiar, although it is a regular
function of their daily lives. An understanding of it may aid those couples who,
due to faulty timing, fail to bring about impregnation, or contrariwise, find it
desirable to reduce it.
It is interesting to notice that as recently as approximately twenty years ago
the details of the phenomenon of the menstrual flow were not completely
understood by the medical profession. We may avoid a description of all the
lengthy, patient, scientific research which went into the study and concentrate
on what is generally accepted.
It is known that the female egg or ovum ripens in an ovary cavity known as the
Graafian follicle. When the egg matures fully, fifteen days preceding
menstruation, the follicle bursts, allowing the egg to enter the Fallopian tube.
This process is known as "ovulation." The egg must be fertilized by the male
sperm within a few hours after ovulation; otherwise the egg perishes. Since the
precise moment of ovulation cannot be determined, twenty-four hours are allowed
for fertilization, although it occurs in less time, perhaps in the neighborhood
of four. The male sperm can maintain its fertilizing vigor at best for only two
days after entering the female body, but it can live considerably longer.
It is known also that the pituitary gland, located in the brain, does, among
other functions, create activity of the uterus. The day following ovulation, a
group of cells called the "yellow body" comes into being on the ovary, nullifies
the control of the pituitary over the uterus, and instructs it to relax and
adjust itself to the arrival of the egg by taking on increased supplies of
Finally, in order to develop normally, the fertilized ovum must imbed itself in
the wall of the uterus. This can be accomplished only when the uterus is quiet
and the membrane relaxed.
Now that we understand the basic facts, let us see how pregnancy takes place, or
how, failing impregnation, a menstrual flow occurs.
Ovulation takes place fifteen days before a period and the egg starts a journey
through the Fallopian tube. It must be speedily fertilized or it dies. The day
following ovulation, the yellow body materializes on the ovary and starts to
exert its influence over the uterus by commanding quiet and directing nourishing
stores of blood to it.
Unfortunately for women, the yellow body automatically issues its instructions
to the uterus on the assumption that a fertilized egg will arrive there.
However, should the ovum perish by reason of nonfertilization, the yellow body
realizes this only ten days later, and then starts to deteriorate. By the
fourteenth day, it has disappeared, whereupon the pituitary, once again in
control, induces contractions in the uterus, causing it to dislodge a lining
consisting of excess blood and mucus. The female thus experiences the beginning
of the menstrual flow.
If, however, a fertilized ovum arrives at the uterus and successfully attaches
itself, the yellow body reacts differently and retains control until the
beginning of labor, when the pituitary again takes command, causing the
contractions of the womb which expel the child.
||FRONTAL VIEW OF FEMALE REPRODUCTIVE SYSTEM
||3. Fimbriated End of Fallopian Tube
These principles make it obvious that a woman can conceive only within
twenty-four hours or less following the ovulation which occurs on the fifteenth
day prior to menstruation. This day, then, is not "safe." Furthermore, since the
spermatozoa can remain vigorous for forty-eight hours, it is apparent that
intercourse occurring one or two days prior to ovulation is "dangerous" because
the sperm, still alive and potent, may be waiting for the egg at time of
ovulation. Thus, the seventeenth and sixteenth days before menstruation are
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Consequently, conception appears theoretically to be possible only from
relationships occurring on the seventeenth, sixteenth, or fifteenth day prior to
ovulation; all other days in the cycle should be "safe." If a woman has a cycle
of twenty-six days and a menstrual period of five days, she has eighteen days
during which she can feel free from impregnation. That is the basis of the
theory of the rhythm. However, there are complications to be considered.
First of all, this theory applies only to a woman with a constant twenty-six-day
cycle, who knows beyond doubt that she is precisely that regular. Suppose,
however, that she ovulates two days sooner or later; no medical man will deny
this possibility. If she ovulates two days earlier than usual or seventeen days
before her period instead of fifteen, she is susceptible to impregnation by
intercourse occurring on the nineteenth, eighteenth, or seventeenth day before
her period. Failing this, her flow will start two days earlier. If, on the other
hand, she ovulates two days later than usual, or on the thirteenth day prior to
the normal date of her period, then intercourse on the fifteenth, fourteenth, or
thirteenth day subjects her to the possibility of pregnancy. Barring this, her
period will fall two days late.
It must be borne in mind that a woman has only her past regularity to depend
upon, and that no one can state positively that this regularity will continue.
The fact is, it will not. Nor is it possible to determine the exact date of
ovulation except by consulting a record of previous periods, since it can be
established only by going back fifteen days from the last day of the cycle.
It seems obvious that if we add two days to each side of the original three
dangerous days, increasing them now to the nineteenth, eighteenth, seventeenth,
sixteenth, fifteenth, fourteenth, and thirteenth we have made an allowance for
any future irregularity of the ovulation date. This is advisable under any
circumstances and advocates of the rhythm themselves suggest it.
However, although we have allowed for an irregularity of two days in either
direction, no one can guarantee against the future possibility of a three, four,
or five-day irregularity. This unexpectedly happens to many women, and the
discrepancy can obtain for as long a period as a week or more. To be reasonably
safe, we may add four days on each side of the original three danger days as a
more than sufficient allowance for a system which is presumed to operate with
far greater scientific consistency. The questionable days now represent the
twenty-first, twentieth, nineteenth, eighteenth, seventeenth, sixteenth,
fifteenth, fourteenth, thirteenth, twelfth, and eleventh days before the usual
termination of the next period. Now, in a theretofore regular cycle of
twenty-six days, five days of which include menstruation, with eleven days
questionable, a woman can feel reasonably safe for ten days.
Although this allowance of an extra four days is considerably more than that
regarded as necessary by one of the research scientists principally responsible
for this enlightening discovery, it still may not be enough. Nature is far too
unreliable, and many unexpected happenings may occur to alter a previously
regular menstrual cycle: a fall, a blow, a shock, an illness, a psychological
explosion, an accident, a change of climate or overstimulation. If a shock can
bring about an abortion or miscarriage, it is not inconceivable that it may
cause a contraction of the ovary and force the Graafian follicle to expel an egg
On the other hand, an egg may precociously mature far ahead of its time. Since
the Graafian cavities and their contents have been developed since adolescence
and perhaps at birth, it is not impossible for an individual egg to mature weeks
in advance or a retarded one, weeks later.
Furthermore, the authorities advise that before applying this principle, the
regularity of the menstrual cycle be carefully recorded and observed for at
least a year, and for an additional four or five months following any subsequent
disruption, in order to determine whether it occurs with absolute consistency.
Obviously, they also recognize the possibility of occasional irregularity.
In addition, it is perfectly possible that nature, which is known to play
unexpected pranks, may decide to release eggs from both ovaries at different
intervals during the same cycle instead of the customary single egg. In fact,
fraternal twins have been born whose relationship was that of half-brothers.
Each had a different father. Nor can anyone say how frequently a pair of eggs
are released at different intervals, because a relationship may not have taken
place at the time one or the other was expelled.
A girl who marries at twenty has roughly twenty-five years before the menopause.
Calculated at the rate of twelve cycles a year, although there will be more, she
undergoes in that span three hundred cycles which we may further reduce by
eighteen while she bears two children. It is not farfetched to assume that out
of the remaining two hundred and eighty-two cycles, nature may deviate at least
half a dozen times. If pregnancy ensues as the result of only three of the six
occasions, the family has been unexpectedly increased.
While it is absolutely true that many people operate under the rhythm principle
to their satisfaction, others have failed to find it reliable. It may be argued,
of course, that the latter were careless in their application, but they deny it.
There is also some difference of opinion among the authorities themselves; some
state that ovulation definitely takes place only on the fifteenth day preceding
the end of the next period, while others assert that it may occur on any one of
five consecutive days. Although both sides have ample evidence to support their
contentions, the layman is unable to resolve the conflict.
The figures used are based on a woman with a simple twenty-six day cycle. Some
women, however, experience a double cycle, such as twenty-six days one month,
and twenty-eight days the next. Still others are subject to a triple cycle of
twenty-six, twenty-eight, and thirty days over a period of three months. While
it is not difficult to work out a table to meet these situations, since only the
extremes are considered, it requires too much calculation, the results of which
still offer questionable security. This is, of course, a matter of opinion.
However, one reliable and valuable fact exists, if the present explanation of
the menstrual cycle is accepted. A specific period encouraging impregnation has
been determined. And it can be utilized or avoided depending upon the desire for
It is appropriate to discuss briefly at this point the practicability of
engaging in intercourse during a men-trial period. Beyond the inconvenience of
it, there is no healthful reason why it shouldn't be practiced. It will neither
lengthen nor decrease the flow as many women believe.
Furthermore, a great proportion of females acquire their strongest sexual urges
at this time. Since the first and last day of the period are usually
characterized by a slight staining only, a relationship, then, is not too
disagreeable. However, should a wife indicate any reluctance to engage on these
occasions, no husband should insist upon it.
This must not be construed to mean that a wife has no duty or responsibility
during this period to satisfy her husband's sexual needs. Many women flow the
better part of a week, and this is a long interval for a man to practice self
control. A thoughtful and devoted mate will not ignore her husband's sexual
moods at this time. On the contrary, she will take pains to anticipate and
satisfy them, if need be, by adequate means at her disposal.
Should she be one of those women whose periods are attended by pain and
discomfort, naturally, no obligation exists. But barring this, any indifference
to her husband's feeling is inexcusable. Considerations of this type on the part
of both partners provide the kind of home atmosphere that cements marriage ties
and encourages general compatibility.