The Ogino-Knaus (O.K) Method of family planning and birth control, often referred to as the ‘Rhythm’ method.

The Ogino-Knaus (O.K) Method of family planning and birth control, often referred to as the ‘Rhythm’ method.

Kyusaku Ogino, of Japan, and Hermann Knaus, of Austria, independently arrived at the same conclusions which form the basis for the family planning method named after them. Their work was promoted by Leo Latz, in his 1932 publication of ‘The Rhythm of Sterility and Fertility in Women’.
Pope Pius XII even gave his Catholic (Zombie Jesus Cannibal Vampire Cult) practitioners ‘permission’ to use this method in the 1950s.
This method simply physically prevents viable sperm from being present in the fallopian tubes at the same time as a viable egg, thus preventing fertilization and conception and pregnancy.
Warning: Even if you follow all the rules and keep perfect records, authorities claim that the Knaus-Ogino Rhythm Method is only 91% effective at preventing pregnancy. So the assumption is that 9 in every 100 women using this method as their SOLE means of birth control, will become pregnant (at some point in their lives? Or each year? Or each month? Can anyone clarify this?).
Disclaimer: I am not a specialist on this subject, nor a doctor. So please do your own research to verify anything written here. But as far as I understand, this makes the O.K Rhythm method among the most effective and reliable methods of birth control. More reliable than condoms. Less reliable than ‘The Pill’, but only assuming to follow ALL the rules that come with any contraceptive pill prescription.
Ideally all men would have viable sperm samples harvested at the prime of their lives, BEFORE they begin engaging in penis in vagina sex, and then undergo Vasectomies, to ensure ZERO chance of unplanned pregnancies.
Men who do not wish to become unplanned biological fathers should consider this option. Especially men who already have biological children.
Condoms are NOT reliable enough if you are conscientious about taking your responsibilities seriously.
For many women condoms are not an option. Their partners may refuse to use them, or be unable to buy them for religious, economic, personal, or social reasons. Some men cannot ‘perform’ using them. Some men have ‘allergic’ reactions to the condom materials.
Many women suffer adverse reactions, and experience undesirable, adverse side effects to the contraceptive pill. Even where there are no immediate health problems, the longer term risks of contraceptive pill use may lead to a woman deciding not to avail herself of this option, even assuming it is available to her, that she can afford it, and that her social and religious beliefs and external controls ‘allow’ this option to be exercised.
Further, using this method means that the moment a woman decides she WANTS to become pregnant, she can begin actively realising her wish. Woman ‘coming off’ the pill often have to wait some time before they are once more fertile.
Many women fall pregnant while taking a contraceptive pill, often due to them taking other prescription drugs at the same time, for health reasons. Some even subconsciously ‘forget’ to take the pill, out of a desire to become pregnant. Many just lie about being ‘on the pill’, as they wish to become pregnant.
But given the general beliefs and practices current at this time, for a woman willing and able to take control of her own reproduction, the Rhythm method appears worth considering. Especially for women with zero access to alternative forms, due to economic, health, social, or religious reasons.
So we shall now explain the basis of the method, and how it works in practice, in detail. Please note that I am not a specialist, and you should be sure to do your own research. All information and opinion is offered here on an ‘all care taken, but no legal liability accepted’ basis. I have gleaned this information from many sources, and attempted to present it in the most easily comprehendible format.
The method, and rationale behind it
A healthy, fertile, woman, between the onset of puberty, and the onset of menopause, can only become pregnant during a limited number of days of her ‘menstrual cycle’. This is key information for anyone seeking to become pregnant, or seeking to avoid becoming pregnant.
A woman is most likely to become pregnant if she has penis in vagina sex a few days before, or during, ovulation.
For all our discussion and calculation that follows, the first day of bleeding that occurs after we begin recording is taken as the ‘first’ day of the ‘menstrual cycle’. Day one, is the day of the first bleeding, in terms of our record keeping.
So if we begin recording today, we will wait until the next bleeding occurs, and mark it down on our calendar as ‘day 1’.
It is common for the next bleeding to begin on ‘day 28’.
World Health Organization (WHO) data indicates that around 80% of menstrual cycles ranges from 26 to 32 days
This method is considered reliable for women whose menstrual cycles over the last 6 months have been between 26 and 32 days long, and have not varied by more than 7 days. In other words the difference between the longest cycle and the shortest may not be greater than 7 days. It it is 8 days or more, or any cycle has been longer than 32 days or shorter than 26 days, the woman must continue keeping records, and wait until her menstrual cycles fall within the ranges just described.
Some women have very predictable, consistent menstrual cycles, while others have quite irregular menstrual cycles.
This method is NOT considered reliable for women whose menstrual cycles are irregular, or shorter than 26 days, or longer than 32 days.
In order to determine if this method of family planning is suitable for a particular woman, someone must keep a continuous record of the next 6 months of this woman’s menstrual cycles. To ensure that they fall within the range, and are relatively regular. Only THEN can this method be considered appropriate, and reliable, for her.
A woman is only fertile for a relatively brief interval within their menstrual cycle just before and after ovulation, when the body releases one or more eggs.
The specific day on which you ovulate depends on your cycle length. This is largely controlled by fluctuations in your sex hormone levels.
Ovulation typically occurs 10 to 16 days after ‘day 1’ of any cycle. If conception does not occur, the woman will have her ‘period’ around 14 days after ovulating.
An egg is only viable for 24 to 48 hours after ovulation.
A woman can only get pregnant a few days before, and within 24 to 48 hours of ovulation.
However as sperm can remain viable in the vagina for up to five days, penis in vagina sex occurring 5 days BEFORE ovulation (the egg being released) can result in conception and pregnancy.
So even if we could precisely pinpoint the exact time of ovulation, we would still need to factor a ‘margin of error’ of at least 5 days to account for the sperm’s potential 5 day viability, and 2 days to account for the ovum’s potential 48 hour viability.
Using a 28 day cycle as an example, ovulation should occur on day 14. The middle of her cycle.
But we must remember that menstrual cycles don’t just vary between women. They can also vary for any individual woman, over time. This is due to variations in the presence of sex hormones in the woman’s body. The balance of sex hormones varies more in some women than others, and for the same women, more in some months than others.
So even where a woman tends to have a very regular, predictable menstrual cycle, we must assume that THIS CURRENT cycle might last anywhere from 26 to 32 days. Or even outside those ranges.
This method is ONLY reliable if we assume that the current menstrual cycle MIGHT be anywhere from 26 to 32 days long.
This assumption would then lead us to assume that ovulation could occur, THIS cycle, any time from day 12 to day 19. So we must take into account the variability of the menstrual cycle as well as the viability of sperm after ejaculation, and of ovum, after ovulation.
Remember, while the egg is only viable for 24 to 48 hours, sperm can survive, as viable, up to 5 days after being ejaculated or artificially placed into a woman’s reproductive tract. Note that technically the term ‘vagina’ refers to the female internal sexual organs.
This means that it is possible to get pregnant 5 days after penis in vagina sex. If that sex takes place 5 days before ovulation, the woman can still become pregnant.
So, taking these factors into consideration, our method considers a woman as potentially fertile, and thus able to conceive, and become pregnant, from day one to day seven, and from day 21 to the start of her next bleeding.
To recap, taking into consideration the possible days of ovulation, and the possible viable lifetime of ovum and sperm, we calculate that women with relatively regular 26 to 32 day cycles must abstain from penis in vagina sex from day 8 to day 21.
Remember that the reported 3% to 25% failure rate for this method is not due to the method itself, but the lack of accurate record keeping, and strict adherence to the rules.
Rule one is that you must wait until you have recorded at least 6 consecutive menstrual cycles. The last 6 menstrual cycles.
I would recommend keeping this on paper, on a calendar, but you can also find many ‘apps’ for mobile phones and computers, which will help you record and track you menstrual cycles.
If the variation between the shortest cycle and longest cycle during past six periods is 8 days or more, you may NOT use this method. You must continue keeping records until the menstrual cycles over the last 6 months do NOT vary by more than 7 days. (Do not vary by 8 days or more).
Further, if any menstrual cycle within the last 6 months lasted fewer than 26 days, (was 27 days or shorter) or more than 32 days (was 33 days or longer), you must use other means of contraception, or abstain from penis in vagina sex, until your last 6 months of menstrual cycles DO fall within the 26 to 32 day range.
You must then continue keeping records, and referring to the lasts 6 months of records to ensure that none of your menstrual cycles lasted longer than 32 days, or fewer than 26 days, and that the variation between the shortest and the longest menstrual cycle was never greater than 7 days ( Never 8 days or more).
The actual calculations you will need to make
Subtract 18 from the shortest of the last 6 menstrual cycles, to estimate the first day of fertility.
Then subtract 11 days from longest recorded cycle of the last 6 months, to estimate the last day of fertility.
Consider this example. If the shortest of her your last 6 menstrual cycles was 27 days, 27 – 18 = 9, and so you must abstain from penis in vagina sex starting from day 9.
If the longest of your last 6 cycles was 31 days, 31 – 11 = 20, you can start having penis in vagina sex again on day 21.
In this particular example, based on the recorded menstrual cycle data for the previous 6 months, our Rhythm method practitioner must abstain from penis in vagina sex from day 9 through to day 20 of her current cycle.
She will then record the menstrual cycle data for the current month, updating her running ‘6 month’ menstrual cycle data, and based on this new ‘6 months’ data set, she will calculate the ‘abstinence’ days for her NEXT menstrual cycle.
The process is ongoing, with the most recent menstrual cycle data being added to the previous 5 months, to give a ‘running’, consecutive, 6 month data set.
Alternatively, if our example was actively and deliberately seeking to become pregnant, day 9 to day 20 is the time frame in which she would want to be making the most 'effort', and engaging in penis in vagina sex leading to ejaculation, or introducing semen by other means, into her vagina.

Some ‘authorities’ also claim that this method is not suitable for teenagers and women approaching menopause. If you have more precise information on this subject, please let me know. It may be that teenagers and almost-menopausal women’s cycles are more erratic than at other times. It may be a lack of confidence in their record keeping fidelity?
These calculations are also valuable for those of you actively seeking to conceive and become pregnant. Day 8 to day 21, inclusive, of your current menstrual cycle, are the days you are most likely to conceive and become pregnant.
If you want to increase your chances of conception even more, then focus on the days you are most likely to be ovulating, based on your past recorded cycles. This should be around the middle of your current cycle. Have penis in vagina sex on the few days before, and then during, ovulation, to maximize your chances of conceiving, and becoming pregnant.
Women are generally most fertile during the 5 days before ovulation, the day of ovulation, and 12 to 24 hours after ovulation.
You can use the last 6 months of records to predict the day on which you are most likely to ovulate during the current cycle.
Alternatively there are methods of determining, more exactly, if you have actually ovulated, if you want or need to be even more precise, such as when using artificial insemination techniques, or if the sperm donor / biological father is only available for a short ‘window of opportunity’.
You can insert a very sensitive thermometer into your vagina before you get out of bed each morning. Hormonal surges at the time of ovulation will increase your ‘Basal Body Temperature’ right after ovulation. By tracking your BBT this way, every day, you will not fail to note the sudden ‘spike’ in BBT at the time of ovulation.
Further, your cervical mucus becomes thinner when you ovulate. So monitoring the color, thickness, and texture of your cervical mucus can provide another indicator of when you are ovulating, and thus most likely to conceive, and become pregnant.
Using these indicators, along with your last 6 months records, and your knowledge that ovulation occurs in the middle of your menstrual cycle, about 10 to 16 days after ‘day 1’ of any cycle, the first bleeding, can allow you to predict and detect ovulation with a good degree of reliability and accuracy.
This will also allow you to predict when you are likely to have your next ‘period’. This may be valuable in planning certain activities. And this will provide you with an ‘early warning’ for any unplanned or planned pregnancy. A period typically occurs 14 days after ovulation if conception has not occurred. So if you do NOT have your period as expected, there is a good chance you have conceived.
However keep in mind that factors such as sex hormone levels account for fluctuations in menstrual cycles, over time. So if you want to be certain, you will need to use a pregnancy test kit. Your period may just be ‘late’ due to sex hormone fluctuations, or other variables. Some women have very predictable, consistent menstrual cycles, while others have quite irregular menstrual cycles.

Note that men experience a similar phenomenon whereby any sperm that has not been ejaculated for the last month or so, will be ejaculated during a 'wet' dream, or heavy physical exertion. Few men ever experience this as adults, as they tend to become sexually excited long before the 'month' is up, and if they have no sexual partner, will masturbate and ejaculate the 'last months' sperm.
And note that both men and women can experience mood swings, becoming more irritable or easily frustrated, and often more aggressive, and emotionally volatile, corresponding to where they are in their current 'cycle'.
Note that ejaculation does not mean a man has experienced an orgasm. A man can ejaculate without having an erection, or an orgasm. Internal stimulation of the prostate with fingers or other means, by insertion into the anus, or by external stimulation of the area between the ball sack and anus, can produce ejaculation, often accompanied by orgasm.
Orgasm in the female is also not required for pregnancy, but may provide the optimal conditions for it.
ANY penis in vagina sex, or exposure of the vagina (female internal sex organs) to semen, can result in unplanned pregnancy. Condoms are only a means of reducing the chances of pregnancy, and the transmission of Sexually Transmitted Diseases (STDs). Condom use only offers 'safer' sex. That is, it improves the odds in your favor. But there is no totally 'safe' sex as such. Any sexual interaction carries with it a risk of transmission of body fluids, and thus pregnancy, or transmission of STD's.
During the ten days or so each month you have calculated as being a time of fertility, you have many other options for sexually gratifying yourself and your partner/s. These include oral sex, hand jobs, fingering, masturbation, mutual masturbation, 'virtual' sex with masturbation, anal sex, 'Spanish' sex (rubbing a penis between the breasts), or simply 'abstaining' in a way that 'increases the lust' so that when the time comes, you have very rewarding and satisfying penis in vagina sex. Without the risk of pregnancy.
Note that the relatively long 'abstinence' interval takes into account the fact that sperm can survive several days after ejaculation, depending on the conditions within the vagina.
Remember that the term 'vagina', technically, refers to the internal sexual organs. In everyday language, it is used to refer to the vulva, which are external parts of the female sex organs. Other external parts include the labia, the inner and outer lips. And of course the 'clitoris', which is partly external, and thus visible, but mostly internal, extending into the vaginal walls. Around 2 inches, along the upper inside wall of the vagina, many women will have an area of great sexual sensitivity often referred to as a 'G' spot. By pressing upwards / outwards towards the stomach around two inches into the vagina, this area can be stimulated with fingers, penis, or other means.
Similarly, by inserting fingers or other 'devices' around 2 inches into the male rectum, and pushing upwards/outwards towards the penis / stomach, you can stimulate the prostate of the man, which often results in strong orgasms and/or ejaculation. This is the equivalent of a male 'G' spot. A similar stimulation can often be attained externally, using a vibrator or fingers placed between the anus and ball sack.
In fact by placing pressure on this area with fingers, just before ejaculation, ejaculate, and thus sperm, can be diverted from the vas deferens into the body of the man, so that he does not ejaculate externally, but internally. However this is not recommended as a reliable form of birth control.
The area between the sex organs and anus, in men and women, is as sensitive as the lips of the mouth, and for some people very sexually stimulating.
The skin around the anus, and the entrance to the anus itself, is also experienced as very sexually arousing and stimulating in many women and men. Some enjoy mere 'rimming' of the outside, while others prefer shallow to deep penetration.