Rhythm method accuracy using NFP charts

[yellow8yellowM]

Is there any study that uses a person’s actual NFP charts and determines what the fail rate of the rhythm method would have been had they used it perfectly? By the fail rate, I mean the rate at which they had relations on a fertile day but thought it was an infertile day, regardless of whether not she got pregnant.

If not, is somebody willing to use their charts, do the math, and report back in? It should be a very easy calculation to do. I bet it is out there somewhere but I have not found the data.

 

[Kelfa28]

The only way to be certain that you made a mistake is when you miss a period and the pregnancy test pops up positive.

Otherwise, you really don’t know exactly when and if you made a mistake each month. Especially with the rhythm method…when you are just flying by the seat of your pants.

I used NFP…STM and clearly made a mistake one month because I’m 5 months pregnant and due in August.

I haven’t gotten a close look at my charts in awhile, they are buried somewhere in the house, but I thought I was regular and ovulated around the same time…clearly I was wrong.

I think if you actually do the charts and take a good look, most women don’t ovulate on day 14 every single month. That’s just not logical to assume this.

I think the odds of getting pregnant, if you aren’t charting, aren’t following any method and using no protection at all is around 15-25%.

 

[pensmama87]

The only way to be certain that you made a mistake is when you miss a period and the pregnancy test pops up positive.

Otherwise, you really don’t know exactly when and if you made a mistake each month. Especially with the rhythm method…when you are just flying by the seat of your pants.

I used NFP…STM and clearly made a mistake one month because I’m 5 months pregnant and due in August.

I haven’t gotten a close look at my charts in awhile, they are buried somewhere in the house, but I thought I was regular and ovulated around the same time…clearly I was wrong.

I think if you actually do the charts and take a good look, most women don’t ovulate on day 14 every single month. That’s just not logical to assume this.

I think the odds of getting pregnant, if you aren’t charting, aren’t following any method and using no protection at all is around 15-25%.

Depending on age and health, of course - as you get older that’s going to go down quite a lot.

Also, to the OP: for most women, charting is going to be very different than using the rhythm method. The rhythm method depends on previous data to predict fertility (like Kelfa says, assuming that ovulation always happens the same day in a cycle, which is really inaccurate). Most couples using modern NFP methods use fertility signals from that day and then they can make a decision from there (to abstain or not abstain, if they’re looking to conceive or not that cycle).

Sometimes I think that a lot of it is that “user error” rates for birth control are calculated simply by fact of pregnancy, but with NFP you also get thrown in the “ah, what the heck,” group (which is where we have been, three times now) in addition to actual misreading or inconclusive fertility signs. NFP users can choose to ignore or abandon the method at any time, which isn’t the case for many forms of contraception.

 

[sadpanda2]

Is there any study that uses a person’s actual NFP charts and determines what the fail rate of the rhythm method would have been had they used it perfectly?

No, because someone who is using NFP is not using the rhythm method.

 

[PaulinVA]

Is there any study that uses a person’s actual NFP charts and determines what the fail rate of the rhythm method would have been had they used it perfectly? By the fail rate, I mean the rate at which they had relations on a fertile day but thought it was an infertile day, regardless of whether not she got pregnant.

If not, is somebody willing to use their charts, do the math, and report back in? It should be a very easy calculation to do. I bet it is out there somewhere but I have not found the data.

It’s known that the rhythm method is less accurate than modern NFP, so what’s the point?

 

[1ke]

Is there any study that uses a person’s actual NFP charts and determines what the fail rate of the rhythm method would have been had they used it perfectly? By the fail rate, I mean the rate at which they had relations on a fertile day but thought it was an infertile day, regardless of whether not she got pregnant.

No. To my knowledge no such “study” of this exists.

If not, is somebody willing to use their charts, do the math, and report back in? It should be a very easy calculation to do. I bet it is out there somewhere but I have not found the data.

Why would someone do this?

 

[Sophie_Lawrence]

I never did a study, but my youngest was conceived on day 24 of a cycle.At the time we were using the Billings method, and I know when he was conceived.

With the “rhythm method”, I should have ovulated around day 14, while day 24 should have been infertile.

That’s why I wouldn’t use rhythm, I’ve never been regular.

 

[white_sheep]

I think the question was different. I could back calculate in a few months. This month is off, she went on a trip and peak was a week later than the last month or two.

It seems to me the question was can you use nfp to determine at what day in your cycle you typically hit peak and use that number instead of 14 to use a more accurate version of the rhythm method? I would think it would be more accurate than the rhythm method. So, I give it a partial yes answer. You can do that, and it’s effectiveness would be better than rhythm but less than nfp.

We have always sort of used some aspects of rhythm, and never really studied or perfected any nfp technique. For instance, staring out we thought we were good until day 12. My brother told me that was a rule or something. Turns out that is incorrect and if she had 28 day cycles or shorter some of those days would probably be fertile. For us I do think it is a good rule that works as she has long cycles and stopping at day 12 until after peak is actually pretty conservative. We now use the clear blue easy fertility monitor to identify peak just to make it easy and have a sort of third party confirmation that she got it right as she has never felt comfortable that she actually knew when peak was. The machine has picked different days for peak than she would have so I really think it was a good idea. If you read the Marquette protocol for using it they incorporate some guessing and extrapolation of prior data to determine peak if the machine isn’t finding one. They say it can miss 8% or one per year on average.

I don’t think it’s crazy, it’s just another tool you can use to help. Try it for a while and see how it works over 6 months of actual observations vs calculated.

 

[white_sheep]

For us it would be a 100% failure rate. That’s off the top of my head, but she has only peaked maybe once or twice that early in the cycle over the last 10 years.

Now could we use an average peak day from observations to use a different number than 14? A rhythm method based on 21 or something instead of 14? Probably. It would be much more accurate, though still not as good as nfp, and since we would still have to be using nfp to determine peak to keep the average based on current information it would be kind of silly. We do incorporate some aspects of guessing based on averages and whatnot.

 

[twoangels]

Is there any study that uses a person’s actual NFP charts and determines what the fail rate of the rhythm method would have been had they used it perfectly? By the fail rate, I mean the rate at which they had relations on a fertile day but thought it was an infertile day, regardless of whether not she got pregnant.

If not, is somebody willing to use their charts, do the math, and report back in? It should be a very easy calculation to do. I bet it is out there somewhere but I have not found the data.

Creighton excludes couples who used known days of fertility from the user failures. These were counted in a separate statistic as the percentage of people who switched from trying to avoid to trying to get pregnant within a year long timespan. As such, they were able to get the user failure rate down to 3.2%. The metod effectiveness has a .5% failure rate.

From what I’ve learned about the failure rates of NFP, is that the vast majority of failures in these studies occur within the first few months. The longer you chart, the more accurately you chart and the more you “get” the method.

The 2007 study on sympto thermal was not an abstinence alone study. They included couples using barrier methods as well as abstinence during the fertile time period. The researchers were actually surprised to find that the condom did cause a statistically significant increase in failures. The method failure rate of that study was about a .5%. The user failure rate, which included unprotected sex during the fertile time was 1.8%.

The Billings Method had a recent study in China. I have not been able to find the actual peer reviewed study with all the details. In that study, they had no method pregnancies and a .5% user failure rate. In earlier studies, Billings has had as high as a 35% user failure rate.

On average, the user failure rate of most methods is 25% and I would say the majority of it is couples having sex on known days of fertility. Granted, I don’t think NFP should be relied upon when learning. From a moral prospective and from understanding that this information has MORE value than family planning, I think every young woman should learn to chart her cycle to some degree around puberty. A mucus alone method would be sufficient to do this. She’ll be better able to predict her period (fewer stained underwear and clothing and all that embarrassing stuff) and have a good health record. And then she should can choose are more specific method. Maybe she wants to learn BBT when she’s older. I don’t know. But whatever symptom she adds and whatever class she takes, it should be a few months before she marries. She should still have charted several cycles. This is completely regardless of if they plan on using the information for family planning purposes or not.

The absolutely worst thing to do is to tell couples they should only learn NFP once they are morally justified (have a serious reason to avoid pregnancy) to avoid pregnancy. This is doomed to fail. My mother experienced 4 unplanned pregnancies in 3 years. She nearly died. It put my parents in a very tough spot.

if women understood their cycles, the Church could spend more time talking about moral theology and less on being the main commercial advertising for natural family planning methods.

 

[Xantippe]

From what I’ve learned about the failure rates of NFP, is that the vast majority of failures in these studies occur within the first few months. The longer you chart, the more accurately you chart and the more you “get” the method.

**That is very interesting.

I’d also add that with experience, one is able to fine tune the rules, making them more conservative as one acquires more experience. For instance, thanks to a baby conceived through marital relations on Day 7 (Day 14 ovulations–woohoo!) almost 11 years ago, we had to declare Day 5 the final day of infertility. More recently, I find myself edging toward perimenopause. My cycles are shortening and I’ve had a number of early ovulations, so we’ve now declared Day 2 the final day of infertility. If my cycles shorten any more, we may have to entirely give up on Phase 1 and maybe even the last couple days of Phase 3.
**

The 2007 study on sympto thermal was not an abstinence alone study. They included couples using barrier methods as well as abstinence during the fertile time period. The researchers were actually surprised to find that the condom did cause a statistically significant increase in failures.

That’s also very interesting.

The Billings Method had a recent study in China. I have not been able to find the actual peer reviewed study with all the details. In that study, they had no method pregnancies and a .5% user failure rate. In earlier studies, Billings has had as high as a 35% user failure rate.

**Presumably, the Chinese are very motivated. **

The absolutely worst thing to do is to tell couples they should only learn NFP once they are morally justified (have a serious reason to avoid pregnancy) to avoid pregnancy. This is doomed to fail.

**Oh my goodness, yes!

That is one of my biggest CAF pet peeves–people that think that NFP is something that you can get perfectly the moment you really, really need it. (When in real life, the more serious your reasons, the less well you are going to be able to cope with learning and getting a track record with NFP.)

I’ve argued before that the possibility of a future need for NFP is in itself a serious reason for newlyweds to at least try out NFP as a live fire exercise (pardon the expression). When you really need it and your life and health depend on it, it would be good to already understand it thoroughly and have confidence in your ability to use it.
**

if women understood their cycles, the Church could spend more time talking about moral theology and less on being the main commercial advertising for natural family planning methods.

 

[yellow8yellowM]

Why would someone do this?

Someone would do this because they do not want to take the effort to chart their temperature and/or mucus, but would like to have some extra assurance that they are not having intercourse during the fertile time.

Apparently somebody did a new study, but I think it was probably a waste of time. They could have taken 10,000 or so real charts and have done the math.

Here is a link to the “recent” study.

irh.org/resource-library/efficacy-of-a-new-method-of-family-planning-the-standard-days-method/

 

[Lorelei12]

Someone would do this because they do not want to take the effort to chart their temperature and/or mucus, but would like to have some extra assurance that they are not having intercourse during the fertile time.

Apparently somebody did a new study, but I think it was probably a waste of time. They could have taken 10,000 or so real charts and have done the math.

Here is a link to the “recent” study.

irh.org/resource-library/efficacy-of-a-new-method-of-family-planning-the-standard-days-method/

What you are suggesting is too much of an extrapolation to be considered sound research. It doesn’t really make any sense. You can’t compare apples and oranges.

 

[yellow8yellowM]

What you are suggesting is too much of an extrapolation to be considered sound research. It doesn’t really make any sense. You can’t compare apples and oranges.

I think there must be a misunderstanding. Here is what I am proposing:

We find somebody who has been charting for several years. In each cycle, there is a predicted time period that is predicted to be fertile. The rhythm method and its variants use the beginning of menstruation, just like the NFP charting methods, to name the first day of the cycle. But the rhythm method simply calculates, for example, days 8-19 as being possible fertile, whereas the NFP methods use bodily signs each day.

What I am suggesting is that for each cycle, you would superimpose the rhythm method predicted 8-19 days onto the chart, and simply see how it corresponds. Then you could make the assessments. You would be able to make these sort of conclusions (I’m making up the results just as an example):

1. 14% of rhythm method predicted infertile days were predicted as possibly fertile using the sympto-thermal method.
2. 2% of rhythm method predicted infertile days were predicted as peak days using the sympto-thermal method.
3. 99.7% of rhythm method pregnancies occurred during sympto-thermal method predicted fertile days.

As I said before, this is incredibly easy to do, if only you had a big enough pile of real charts to use to calculate with. And it would be incredibly informative.

 

[Lorelei12]

I think there must be a misunderstanding. Here is what I am proposing:

We find somebody who has been charting for several years. In each cycle, there is a predicted time period that is predicted to be fertile. The rhythm method and its variants use the beginning of menstruation, just like the NFP charting methods, to name the first day of the cycle. But the rhythm method simply calculates, for example, days 8-19 as being possible fertile, whereas the NFP methods use bodily signs each day.

What I am suggesting is that for each cycle, you would superimpose the rhythm method predicted 8-19 days onto the chart, and simply see how it corresponds. Then you could make the assessments. You would be able to make these sort of conclusions (I’m making up the results just as an example):

1. 14% of rhythm method predicted infertile days were predicted as possibly fertile using the sympto-thermal method.
2. 2% of rhythm method predicted infertile days were predicted as peak days using the sympto-thermal method.
3. 99.7% of rhythm method pregnancies occurred during sympto-thermal method predicted fertile days.

As I said before, this is incredibly easy to do, if only you had a big enough pile of real charts to use to calculate with. And it would be incredibly informative.

I do believe I understand what you are getting at, however I still don’t really see what the point would be. Not only would you have no way of controlling for most variables, but it’s also already fairly well known that the rhythm method isn’t reliable for most women. It’s not that previously collected data has no value, but rather that in your proposed study you’d have no way of knowing things such as whether the couple was trying to conceive, trying to avoid, or neither; or how long a participant’s cycle length tends to be normally; or whether she was sick; or how she took her temperature; and so forth. All of these things and more are addressed in a study with assigned participants, so that any outcomes and conclusions drawn from results are more sound. You mentioned that the study you cited was a “waste of time”, but it is much more informative and scientific than analyzing a bunch of charts where things are not standardized. So I am not sure what you mean when you say your proposed study would be “incredibly informative”. How? It seems like it would just reinforce what everyone already knows, while using questionable data.

 

[Rau]

Is there any study that uses a person’s actual NFP charts and determines what the fail rate of the rhythm method would have been had they used it perfectly? By the fail rate, I mean the rate at which they had relations on a fertile day but thought it was an infertile day, regardless of whether not she got pregnant.

If not, is somebody willing to use their charts, do the math, and report back in? It should be a very easy calculation to do. I bet it is out there somewhere but I have not found the data.

The effectiveness of NFP (sympto-thermal) and Rhythm (Standard Days) are included in the table in the following article.

en.m.wikipedia.org/wiki/Comparison_of_birth_control_methods

With perfect use, Rhythm has a 5% failure rate and NFP roughly 0.6%

This does not answer your specific question, but the relativity in effectiveness of the methods is clear.

 

[yellow8yellowM]

I do believe I understand what you are getting at, however I still don’t really see what the point would be. Not only would you have no way of controlling for most variables, but it’s also already fairly well known that the rhythm method isn’t reliable for most women. It’s not that previously collected data has no value, but rather that in your proposed study you’d have no way of knowing things such as whether the couple was trying to conceive, trying to avoid, or neither; or how long a participant’s cycle length tends to be normally; or whether she was sick; or how she took her temperature; and so forth. All of these things and more are addressed in a study with assigned participants, so that any outcomes and conclusions drawn from results are more sound. You mentioned that the study you cited was a “waste of time”, but it is much more informative and scientific than analyzing a bunch of charts where things are not standardized. So I am not sure what you mean when you say your proposed study would be “incredibly informative”. How? It seems like it would just reinforce what everyone already knows, while using questionable data.

I retract my previous statement that the study was a waste of time. It was a gross exaggeration.

But I am not trying to answer all of the questions you are proposing. I only want to answer one thing: Using the rhythm method, how many days would it wrongly-predict infertile days, as defined by using the sympto-thermal method?

What I am going to do it try to find the data from the original NFP published papers and do the math on that data. I’ll report back in when I’m done.

 

[Lorelei12]

I retract my previous statement that the study was a waste of time. It was a gross exaggeration.

But I am not trying to answer all of the questions you are proposing. I only want to answer one thing: Using the rhythm method, how many days would it wrongly-predict infertile days, as defined by using the sympto-thermal method?

What I am going to do it try to find the data from the original NFP published papers and do the math on that data. I’ll report back in when I’m done.

The questions I mentioned are not research questions- they are questions about variables that need to be taken into account in such studies. In order to answer your question and draw any meaningful conclusions, those things should be taken into account. I am simply saying that you will not be able to generalize any of your “results” to the population- your “sample” will not be representative of anything if you pull random charts from places.

For instance, suppose you found a bunch of charts where the woman’s cycle was always exactly 28 days. You’d get a nearly 100% accuracy rate. We know that’s not right. You have no way of knowing whether the charts you randomly find online are from women who have PCOS, are breastfeeding, have been sick recently and had their cycle thrown off, have come off contraceptives, etc. etc. That is why researchers study these things in a controlled, scientific way. So that they can make claims that are based on what is known and controlled for, and accurately generalize to the population.

 

[1ke]

Someone would do this because they do not want to take the effort to chart their temperature and/or mucus, but would like to have some extra assurance that they are not having intercourse during the fertile time.

You would have NO such assurance. Any given month could have its own pattern, it’s own deviation from “averages”. Calendar rhythm is simply averages.

Those who are not actively charting their CURRENT fertility would be said to have abandoned the method in any of the scientific methods.

 

[alphawoman]

What I would like to see is a large prospective study of phase 3 only method and user failure for the major methods (Creighton, ST, Marquette) for people with reason to avoid indefinitely, with survival analysis going out in the long-term (think 10 years). I also think the NFP cause would be aided by large-scale specialty studies of postpartum (past the first 12 months) and perimenopause subpopulations.

To Marquette’s credit, it has been a leader in postpartum publishing, but its studies’ sample sizes are so small that their efficacy rates vary across studies. STM also has a study from the 1970s which could do with some updating based on method adjustments. The Church, given its enormous wealth, would do well to invest $5-10 million each in a selection of really robust clinical trials in these areas. This is a topic that touches EVERY married Catholic, such that the per-Catholic costs of, say, $100 million in clinical trials would be ten cents. Ten cents to potentially save a soul that would otherwise contracept–and potentially children who would otherwise have been aborted by IUD or BCP use–is an extremely good value for money! I would personally donate to the Church to support such an initiative.