The 2007 NFP Study, revisited

I was just referring to this European study of Natural Family Planning methods that was completed in 2007, and I looked up my blog article on it to double check the numbers (here’s a link to the abstract of the actual study). While writing the elaborate reply to the person, I decided to just write a blog post and link it. 🙂

First, a word on “failure” of birth control methods. When they talk of “failure” of a birth control method, they mean that, when they say “X%” failure rate, they mean that, out of 100 couples who use the given method for a whole year, X women will become pregnant.

Secondly, it is a constant irritation to NFP advocates to have NFP dismissed as “rhythm method” or “modified rhythm method.” The article from _Scientific American_ linked above is so biased, it’s disgusting, and the only comment, after 4 years, is someone challenging whether the study was peer reviewed(!)

It flabbergasts me that liberals, who are “all about science” when it comes to Darwin, “Global Warming” and embryonic stem cell research, deny the science when it comes to women’s fertility. Liberals, who insist that we need to know everything about dinosaurs, the prevailing theories about the origins of the universe, and what’s inside an atom in order to function as ordinary human beings, balk at the idea that a woman should know how her own body works and be able to keep track of her own fertility.

Liberals, who insist that people should have self control about tobacco, insist that people can’t have self control about sexuality.
Liberals, who insist on teaching “safe sex,” and the importance of using a condom “correctly” or making sure a woman takes her birth control pills every day at the same time, think it’s an unbearable burden to ask women to take their temperature every morning, or to check their cervical mucus or to pee into a cup and stick in a test strip to find out if they’re ovulating. . . .

Liberals do not want to give women control over their own fertility. The very people who speak of women “owning their own bodies” and speak of “women’s rights” want women to listen to some doctor tell them what to do with their bodies. They do not want to empower women with knowledge of fertility.

The very people who talk about how important sex education supposedly is do not want to teach the most important thing people should know about sex.

Another preliminary note. There are three sets of “days” at play in understanding these issues. One is the number of days when it is possible for a woman to get pregnant. When cervical mucus is present, sperm can survive in the vagina for about 3 days (some texts say as many as 5, but most agree it’s 3). During the days leading up to ovulation, the woman’s body releases increasing amounts of Luteinizing Hormone (LH). The maximum amount is released on what is called “Peak Day.” In an ordinary cycle, the big shot of LH is followed up by a release of something called FSH, follical stimulating hormone, which actually triggers the release of the egg. There’s some relationship with FSH and progesterone (I’ve read a lot of stuff on NFP over the years but can’t always cite it, and I’ve combined material from a lot of texts).

One of the main problems of NFP “failure” comes from the problem of what’s called “false peak”–the LH is released, so all the external signs indicate ovulation, but FSH isn’t released, so no egg. The reason I advocate Marquette Model is that the ClearPlan machine tests for FSH as well as LH and gives a more precise reading to prove when ovulation occurs.

In any case, once the LH surge/peak day happens, then there is a 48 hour window for the FSH surge and the release of the egg. The egg will live for 24 hours if it isn’t fertilized.

The number of days required for abstinence in NFP depends upon the method and what methods of testing are involved. An ideal method of of NFP would be able to predict when ovulation was likely to occur and isolate ovulation exactly. ClearPlan makes a test which comes close to doing this, but the FDA won’t allow it in the US, and it’s rather expensive to mail order from England.

Again, you’ll hear different ideas of “days.” There are in reality only 4 days per month when intercourse can lead to pregnancy: the 72 hours before and 24 hours after the egg is released.

However, barring the perfect NFP method, that can be expanded to up to 2 weeks of abstinence. I don’t remember sympto-thermal’s rules well enough, but let’s just say 10 days.

OK, so back to the study.

The study showed the following, according to its abstract:
[blockquote]After 13 cycles, 1.8 per 100 women of the cohort experienced an unintended pregnancy; 9.2 per 100 women dropped out because of dissatisfaction with the method; the pregnancy rate was 0.6 per 100 women and per 13 cycles when there was no unprotected intercourse in the fertile time. [/blockquote]

This article, from Science Daily, was the one I referred to in my original post (though the original link was lost when I moved to WordPress from Blogger):
[blockquote]In the largest, prospective study of STM, the researchers found that if the couples then either abstained from sex or used a barrier method during the fertile period, the rate of unplanned pregnancies per year was 0.4% and 0.6% respectively. Out of all the 900 women who took part in the study, including those who had unprotected sex during their fertile period, 1.8 per 100 became unintentionally pregnant. . . .
Of the 900 women, 322 used only STM and 509 women used STM with occasional barriers during the fertile time. Sixty-nine women did not document their sexual behaviour. Out of the women who documented their sexual behaviour and abstained from sex during their fertile period (“perfect use”) the unintended pregnancy rate was 0.4 per 100 women and 13 cycles [2], and 0.6 for women who used STM plus a barrier if they had sex during their fertile period. For cycles in which couples had unprotected sex during the fertile phase, the pregnancy rates rose to 7.5 per 100 women and 13 cycles. The drop-out rate from using STM for reasons such as dissatisfaction or difficulties with the method was 9.2 per 100 women and 13 cycles, and compared well with the drop-out rates from other methods of family planning, which can be as high as 30%, although direct comparisons are difficult due to methodological problems. “This demonstrates a fairly good acceptability for this particular FAB method,” said Prof Frank-Herrmann.
[/blockquote]

A key point here is that “fertile times” means “thought they were fertile.” It refers to charting fertility. If you’re saying, “.4% of couples who had no intercourse during fertile time had a pregnancy,” and “fertile” means “fertile”, then the only conclusion, Dr. House would tell us, is that the women were going off and having sex with other men.

However, they mean that the people *charted* fertility and had a pregnancy. So that means there’s a .4% error rate in charting itself: out of every 250 couples who use sympto-thermal NFP for a year, 1 couple will have a pregnancy that results from misreading the signs and making a mistake in charting.

When considered by themselves, couples who had intercourse during fertile times had a 7.5% chance of getting pregnant. The researchers suggested that this came from “moderately cautious” use of NFP–only abstaining during the days of peak fertility. It may also indicate that the chances of any given act, even in fertile times, resulting in pregnancy are kind of slim.

Now, what we *don’t* know is how often the couples were engaging in marital rights. Numerous studies have indicated that NFP couples have intercourse more frequently than others, but the average seems to be about once or twice a week. We’ll take the high estimate and say twice a week.

“Fertile” period for sympto-thermal purposes, is day 6 or when the woman first detects mucus (whichever comes first) until day 3 after Peak Day.

If the woman ovulates on day 14 in a 28 day cycle, then that’s exactly 11 days of abstinence out of 28 (again, in terms of those who complain that is too much time to wait, compare to married couples who say they only have intercourse once or twice a month, particularly when the woman’s sex drive has been killed by the estrogen pill).

Again, 11 days of abstinence due to potential fertility, and only 4 days of actual fertility, which in the case of .4% of the couples, those don’t overlap.

So for those who had intercourse sometime in those 11 days (and the data weren’t specific enough to say), 7.5% got pregnant.

Now, let’s look at those who used barrier methods during those 11 days. This is where I think I made a mistake 4 years ago. I have often referred to this study because the rate of pregnancy was .6% among those who used barrier methods during charted “fertile times” and .4% among those who abstained. I was thinking that meant that the rate was 150%. Where I made a mistake was forgetting that the same rate of failure in the .4% is in the .6%.

We’ve established that the failure rate of the method to accurately detect ovulation is .4%, so that needs to come off the top of the other percentages. For those who used condoms when they *thought* they were fertile, it was .6%, but taking off the .4, that gives us .2% of couples getting pregnant because of condom failure as opposed to NFP failure (maybe higher, but that will do).

For those who had intercourse during the 11 days of potential fertility, there was a 7.5% pregnancy rate, and if we take off the .4, that reduces it to 7.1%.

This is the key. 7.1% got pregnant because they had “unprotected intercourse” during charted fertile times, and they charted accurately. .2% used condoms during charted fertile times, and charted accurately.

It is very important to get this down right: 7.1% of unprotected sex during accurately charted fertile times led to pregnancy, and .2% of “protected” sex during accurately charted fertile times led to pregnancy, so that means that 6.9 of those 7.1% would have been prevented by condoms. 6.9/7.1 = 97% That means that condoms are 97% effective *if used during fertile times*.

This has two equal and opposite things to tell us about condoms and other barrier methods.

On the one hand, in terms of preventing STDs, they may actually leak far more than is reported, since the only way to *know* if they leak is if they result in pregnancy, and this is the only study that shows their use during fertile times.

On the other hand, even the couples who used condoms or who had unprotected sex during fertile times were still using NFP information to try and avoid the peak days. So maybe they had sex on day 11, thinking they had time, but the sperm made it to day 14, or maybe the wife ovulated a day early or something. Most people don’t take these factors into consideration. Again, the researchers were surprised at how *low* the pregnancy rate was for unprotected sex.

According to this chart, the “failure rate” among most barrier methods is about 5%, so that tells us that those methods are more effective when practiced in conjunction with fertility awareness, which reaffirms that this is knowledge all people should have.

Look at the statistics on some of these methods. Now, for every method, there’s “normal use” versus “ideal use.”

People are fond of saying “NFP doesn’t work.” You’ll hear lots of people who say, “I tried NFP, and I got pregnant, so I started using birth control.” Yet plenty of people get pregnant on birth control. I once met a lady who conceived her second son less than 2 months after her first son was born. She was breastfeeding, and taking the Pill, and she had an IUD, and she got pregnant.

We’re told that NFP is too demanding, yet the Pill requires a woman to take it at the same time every day, and to have the exact dose for her body. Condoms have to be used “correctly.” So do other barrier methods.

“Failure” of IUDs is .2% (and when inter-uterine devices “work,” they prevent a “fertilized egg”, aka an embryo, aka a baby, from implanting in the uterus–“It’s not an abortion because pregnancy hasn’t started,” they tell us). This is slightly better than tubal ligation at .5% “failure rate”.

The male condom, used improperly, has a 15% failure rate, and a 2% failure rate used properly. The “female condom” (often heralded is a way to keep women from getting pregnant if they happen to be raped) has a 21% failure rate if used “incorrectly” and 5% failure rate used correctly. Diaphragm is 16 percent if incorrect/6% if correct.

There are so many other variants, it’s not worth saying. The chart isn’t entirely accurate, as it states the “failure rate” of “improperly used” NFP as 25% but only because it’s using the “failure rate” of the rhythm method.

The great myth is that somehow NFP is more demanding than any of these other methods or somehow they are perfectly accurate.

People use condoms, diaphragms, etc., thinking that these things are fool-proof “birth control,” and, worse, they use them thinking they’re fool-proof protection against STDs. Of course, they’re definitely not “fool-proof,” since responsibility and careful attention and self control are required for most artificial birth control methods to be maximally effective. And even when maximally effective, that’s no better than 2%.

15% if used improperly, as most people use it. For every 100 people who use condoms for a year, 15 pregnancies will result. That means that for every 100 people who use condoms to prevent STDs, 15 will get STDs. Yet we’re told condoms prevent AIDS.

Even 2% failure rate is unacceptable if we’re talking about STDs.

Similarly, while some critics might point to the 9% dropout rate in the German study, the researches point out in the Science Daily article that the average “drop out rate” among users of any given birth control method is 30%.

There is no 100% effective form of birth control except abstinence, and every argument waged against NFP could just as easily be made against any form of artificial contraception.
This study proves several things:
1) that NFP is actually more effective than the Pill (.4% versus 1.8%)
2) that NFP even used in conjunction with barrier methods improves the effectiveness of barrier methods.
3) that barrier methods leak

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