THE TIME CHOICE METHOD FOR GENDER-PLANNING
Since the beginning of human history exists proof that people have tried to influence the sex of a desired baby. It was, however, not until this century that realistic possibilities had been discovered, such as chemical influence on the two kinds of sperms, or their artificial separation followed by artificial insemination. It was only 25 years ago that a completely natural method originated, which I call Time Choice Method. Begetting a desired baby with this method is like any begetting act, and the only difference lies in the fact that one has to determine a special day for this act within the menstrual cycle of the mother to be.

1. OVERVIEW
Permit me to start with a brief overview. The story starts with my dissertation. In it I analyzed the question of why always and everywhere more boys are born than girls, although the process of cell division necessarily produces the same number of gender-determining germ cells with X- and Y-chromosomes. One answer seemed to be the hypothesis of the American gynecologist Shettles which he deduced from especially high preponderance of boys in artificially procreated children. His hypothesis was that male-carrying sperms travel faster to the ovum than to those producing female children, but that they do not live as long. This hypothesis lent itself to developing a plausible theoretical explanation of the phenomenon of the so-called sex ratio of births It the hypothesis could be proven to be correct, however, then the gender of a desired child could be planned:
On the day of ovulation intercourse will produce a boy because here a male-carrying sperm will win the race to the ovum. Two days preceding ovulation a girl will be fathered because only the longer lived female-carrying sperms can wait long enough for the ovum.
There still is no way to ascertain in advance the day of ovulation with sufficient precision. In order to determine it I used the evidence on the span of fertile days which may be calculated with the help of the Knaus-Ogino method. My recommendation is therefore to move procreation to the lower end of the span of fertile days if a daughter is desired and to the upper end of the span if a son is desired. In this way either the gender-specific procreation day is found or no pregnancy will occur during this cycle because there happened to be another length of the cycle than the assumed shortest or longest duration.
A research project founded by the German Research Association proved that with correct application this method can achieve high rates of success. But it also showed that the majority of interested people are overtaxed by the necessary calculations regarding cycle length and numbered cycle days, i.e. that they make calculation errors. In the meantime aids have been developed, however, which obviate any kind of calculation and thus prevent calculation errors.
The research project also yielded the secondary finding that the Knaus-Ogino contraception method is much more reliable than generally believed, provided several conditions for its application are taken into consideration and the decisive days are found correctly. Since the aids mentioned may facilitate this or even guarantee this, they also make natural contraception more reliable. Combined with another method of contraception it achieves the same high margin of safety as the pill.

2. THE THEORY
A child's gender is decided at the time of fertilization, depending on whether a male or female carrying sperm has penetrated the ovum. The pair of gender chromosomes is XX for females, implying that following ripening division the ovum always contains an X-chromosome, whereas from the XY pair of male gender chromosomes the cell, following ripening division, contains either X or Y as the gender chromosome. Fig.1 shows the possible combinations and indicates that theoretically the same number of both sexes should originate. In contrast. the statistics show a sustained preponderance of male births.

fig 1

Fig. 2  presents the sex ratio of births in Germany since 1900. Like in all other countries there are at least 5 more boys for every 100 girls born. Since miscarriages and still births contain an even higher proportion of boys than do live births, the preponderance of boys must be even higher at conception than at birth. It is not equally high for all sub-groups of the population, however. Thus it is lower for illegitimate births than for legitimate births, it is higher for first-born than for later ones, it varies according to religion or to profession, and - particularly puzzling for a long time - was the increase in the male share among warring populations in times of war. This chart shows a highly significant increase in the male share of births during the two world wars, and a decline after the wars had ended.

fig 2

The gender proportions in new-born in
Germany in the years 1900 up to 1985.
No dates available for the time during world war II.

Source: Statistisches Reichsamt, Statistisches Bundesamt

With the help of the before-mentioned hypothesis regarding the different characteristics of the two kinds of sperms the preponderance of male births may be explained easily, if one assumes that the speed advantage of the male carrying sperms is more important than the disadvantage of the shorter period of capability to fertilize. Differences in the level of the sex ratio may then be traced to variations in the frequency of cohabitation during the fertilization period. If, for example, as the result of multiple intercourse during the fertile days the faster male-carrying sperms, which were ejaculated closer to the time of ovulation, are competing with the slower female-carrying sperms from past cohabitation, then, although chance will largely determine the child's gender, the younger male-carrying sperms will more frequently win out over the older female carrying ones. Fig. 3 supports such an assumption. it shows a correlation between the frequency of intercourse per week according to Kinsey and the sex ratio of births in Germany depending on the parents age. It is a well known fact that the frequency of sexual contact declines with age, but so declines the preponderance of boys, and the correlation is almost linear.

fig 3
Relation between age of parents, frequency of sexual contact and excess in the birth rate of boys.

Source: Kinsey- Report, Statistisches Bundesamt

It is also well known and undisputed that in special circumstances determined by exogenous factors, especially by an extraordinary psychological experience of the woman, ovulation may occur one to three days before its normal time. This is called provoked ovulation in contrast to timely ovulation. Such an experience of the woman may, e.g., be her very first sexual intercourse, her first one with the child's father or her first one following a long separation . If ovulation is produced by a first intercourse during the fertile days, procreation always happens on the male-fathering day. This explains, for example, the higher sex ratio among first born or its increase in times of war by soldiers on home-leave or by returning prisoners of war.
Whenever a hypothesis is able to explain the statistical evidence, then the statistical evidence in turn provides the statistical verification of the hypothesis. If, furthermore, the hypothesis is correct of the different properties of the two gender-determining types of germ cells, then it may also be utilized for gender-planning.

3. THE METHOD OF GENDER-PLANNING
It follows directly from the before-mentioned hypothesis that on the day of ovulation a boy may be fathered, because here the faster male carrying sperms reach the ovum before the slower female-carrying sperms. Likewise, two days before ovulation a girl may be fathered, because only the longer-lived female-carrying sperms can wait that long for the ovum. The sperms' maximum capability to fertilize within the woman's body is assumed to be three days, but this period only occurs In exceptional cases, while 2 days is usual.
This implies that the planning method cannot be based on the maximum period. But how does one know, if a girl is to be fathered, that the day after tomorrow is the day of ovulation so that it must be fathered today? The same uncertainty applies in the case a boy is to be fathered: Is today the day of ovulation ? In some cases this may possibly be determined by mittelschmerz or by maximum spinnbarkeit of the cervical fluid. Reliable information on ovulation, e.g. by measuring the basal body temperature or by means of the spinnbarkeit test, is only available after the fact and then it is usually too late for inducing a pregnancy.

The high regularity of the distance between ovulation and the start of the following menstruation suggested a promising solution. This distance is almost always exactly 15 days for almost all women. Exceptions may be ascertained by measuring the temperature or by other cycle analyses, but they seem to be so rare as to be ignored as long as the length of the cycle does not fluctuate by more than five days. Then one can count back 15 days from the date of the first menstruation day in order to know when ovulation took place. By doing this over several months - at best over an entire year in order to cover possible seasonal fluctuations as well - one may determine the earliest and latest date of ovulation after the start of the menstrual cycle. From these findings Knaus and Ogino developed their recommendations of how to determine the fertile days depending on the range of fluctuation of the menstrual cycle.
If there is sexual intercourse two days before the earliest possible date of ovulation, i.e. at the low end of the span of fertile days, and then there is no intercourse during the other fertile days, the child has a high probability of becoming a girl or there is no pregnancy at all because the cycle was not the shortest one observed. Correspondingly there is a high probability to conceive a boy, if there is intercourse on the latest possible day of ovulation and there is none at all during the preceding fertile days. Again, there is no pregnancy during this cycle, if it is not the longest one observed. Thus the time-choice method of gender-planning as described to me is nothing else than a combination of the Shettles hypothesis and the findings and recommendations of Knaus and Ogino.

4. EMPIRICAL TESTING
After my dissertation was finished, a German magazine offered me an opportunity for testing the methodological considerations for gender planing. Pregnant women who expected a child in December 1966 and were able to specify the date of conception, could ask, on the basis of these facts and the dates of their menstrual cycle, for a forecast of the gender of their expected child which was later compared to the actual sex of the child. Since at that time gender diagnosis with the help of ultrasound had not been developed, and the women participating in the test could not possibly know the gender of their child, the participants met the requirements of a random sample. The results exceeded my boldest expectations.
In 1970 Shettles had published his findings as a book on gender-planning. He failed to conceive of the idea with the upper and lower bounds of the fertile days. In view of a very imprecise ability of forecasting the date of ovulation he recommended as an additional determinant the alkaline or acid treatment of the cervical milieu. This is a method of gender determination which has been known since the 1930s but is considered problematic and dangerous by some experts.
Since my method of gender-planning requires no manipulations at all, I deemed it worthy of publication. Thus in 1970
I published my book "Desired Child - Son or Daughter".

From 1973 to 1976 the German Research Association, using this book, provided the means of large-scale testing of the method of gender-planning described therein. More than 3000 interested couples received this book free of charge as preparation for the necessary behavior for gender-planning. In return they had to consent to answering questions on their motives for desiring the particular gender for their child, to sending in the data on the menstrual cycles and notes on the days with intercourse during the start of the pregnancy as well as to informing us of the actual sex of the newborn. Fig. 4 shows a pregnancy statement for a desired girl. Represented is a menstruation calendar according to Knaus which yielded the day of ovulation at the earliest on the 12th day and at the latest on the 16th day of the cycle. Intercourse took place on the 10th day of the cycle,i.e. exactly two days before the earliest possible date of ovulation. Since the next intercourse mentioned was not until the 18th day of the cycle and thus outside the range of fertile days, the conditions for the desired female baby were optimal, and in this case the wish came true.

After several hundreds of births there was clear evidence that with correct behavior the ratio of success was 80 % for a boy-wish and 90 % for a girl-wish. But the evidence also showed that in the beginning more than half of the participants had made errors in calculating the menstrual calendar. The most frequent mistake was to calculate the 15 days from the length of the cycle rather than from the first day of menstruation which adds one day to the length of the cycle. But the latter, too, was calculated wrong sometimes, and it was Impossible to determine whether even a correctly chosen cycle day was transferred correctly to the calendar date.
Many believe that e.g. the 10th day of the cycle would fall on the 12th of March, if the first day of menstruation is on the 2nd of March, while the correct answer is the 11th of March. The mixture of ordinal and cardinal calculations seemed to have overtaxed most of the people interested In the method. This is not surprising, considering that Professor Knaus published calculation errors in his instructions for more than 30 years, errors which even today are repeated by experts in writings on contraceptive methods. In a supplement to my book, even before the completion of the research project, I explicitly pointed out the major risks of making errors and recommended two different methods of determining the critical days. This led to a having of the share of proven errors on application of the method, but it still remained quite high.
This did not change until a special movable calendar had been developed, which shows the critical days as calendar dates just by marking the date of the first day of the cycle. This makes any calculation superfluous and hence eliminates all calculation errors. Experience based on this calendar shows that, given correct behavior which is measured in terms of 10 criteria of following the instructions, there has not been a single failure with respect to a desired daughter and only one with respect to a desired son in a sample of 26 cases. This reflects an unbelievable high theoretical ratio of success, unbelievably especially in view of the known capriciousness of nature which does not know 100-percent results.
The effectiveness of the proven gender-planning method is lately also supported by the German population statistics. In 1974 Westoff and Rindfuss published a study on the gender preferences of American families in the journal Science. They stipulated that in the early years following the introduction of such a method there would be a rise in male births, followed by a wave of more female births. Their reasoning was that most families want children of both sexes, but they want a son first and a daughter only thereafter. Since the mid-1970s the German statistics on births show exactly these fluctuations: Short-term positive and negative extreme values of the gender ratio of births have doubled compared to past observation outside of war periods, and positive swings may be observed always one to two years following intensive media coverage of gender-planning possibilities.
Today there remains no doubt about the effectiveness of the method. For those who have the necessary patience for the planning preparations and for the planning itself until pregnancy is achieved, the time-choice method provides a reliable and completely natural method. If application was initially impaired by the risk of calculating errors, the latter may be prevented today by the use of aids. The improvement of such aids renders application of the method increasingly simple.

5. GENDER-PLANNING AIDS
Once it had been established that the time choice method of gender planning was functioning excellently if applied properly, but that errors are easily and therefore frequently made in recalculating cycle dates into numbered cycle days and then into calendar dates, the development of a system based entirely on calendar dates suggested itself.
Meantime the Swiss-Lady watch is developed and is avoiding all calculation errors made in past.

6. IMPROVED NATURAL CONTRACEPTION
The time-choice method of contraception is said to have a relatively high failure rate. Different studies state a pearl index of 10 to 20 %, referring to the number of pregnancies if 100 women practice the method for one year. There is agreement among scientists that these values result primarily from application errors. Account must be taken, however, of the fact that the regularities of ovulation and the following menstruation period, on which this method is based, are subject to exceptions, as ovulation may occur earlier or later than usual by external influences. In addition, the interval to the following menstruation is not always constant. The research project mentioned before has shown, however, that changes in the cycle lengths do not occur under normal marital conditions. The same is true for deviations regarding the position of ovulation within the cycle if the latter does not fluctuate by more than five days. It must be kept in mind that the proven failures of the method were restricted to cases with an unambiguously determined day of procreation, and the latter could only be known for instance in cases of rape or a soldier's brief leave from the front, i.e. under extraordinary conditions.
Obviously the method is not suited for extraordinary life circumstances, nor for young girls or menopausal women. But its biological exceptions are so few in normal marital life that the failure rate is unlikely to be higher than for other common methods of contraception. It is therefore an excellent method of contraception for couples who still want children, but want to postpone the birth of their next child. It is well suited as a combination method for all other cases in which pregnancy is to be prevented, but where the pill cannot or should not be taken. If reliance is placed on other means of contraception like condoms or chemical compounds on the green days of the calendar or the watch, with abstinence on the other days or with a combination to two other methods on the fertile days, then the same reliability may be achieved as with the pill, it is highly improbable that at the same time there is a biological deviation in the behavior of the cycle and the other contraceptive method also fails, or vice versa.

Thus the findings are not only a way for natural gender-planning but also for encouraging natural contraception.

Dr. Otfried Hatzold