NFP - accuracy?

I was reading an article (don’t remember where) that this doctor, a supposed expert on birth control, said that NFP is only 40% effective when used properly. I had understood it to be 98% effective when used properly. What is the accuracy rate?

Which method was he referring to? What studies did he cite?

Each method is distinct. Doctors have studied each method. You should research Sympto-Thermal, Marquette, Creighton, and Billings individually. These clinical studies do show very high effectiveness.

Websites citing supposed effectiveness rates of various methods of contraception typically lump NFP in with “no method”, “rhythm method”, “fertility awareness method” and sometimes with “withdrawal” as well.

I haven’t ever seen any curated effectiveness rate statistics that list the natural family planning methods by method and separate them out from these other completely unreliable unscientific methods. I mean “no method” really brings those stats down, don’t you think?

What method? NFP is kind of a catch all term and many falsely equate it with the “Rhythm method” Which is actually a form of NFP but not a very accurate one.

I don’t remember any specific method cited in the doctor’s wording. Neither did he cite any studies, which made me wonder.

Not much of an “expert” if he doesn’t even know about different methods of NFP and uses the term as a generic term. Assuming he even knows about other methods it is at best dangerous and careless terminology for a “doctor” to use.

Also, as someone who has practiced several NFP methods, I can say that 40 percent is laughable.

40 percent is probably more like percentage of people that use ABC who end up with a baby anyway!

Often “experts” feel comfortable stretching the truth if they feel their end goal (having all women chemically sterilze themselves) is just. I vividly remember a supposed obstetrician coming to talk to my health class about pregnancy in high school. Actually, the only helpful information she gave us about pregnancy was that pregnant women shouldn’t drink. The rest of the talk was about not getting pregnant. I specifically remember her telling us that a woman can get pregnant at any point in her cycle. I remember because I raised my hand and asked for clarification, as we had studied the cycle and that didn’t mesh with what we had learned. She adamently restated that a woman can get pregnant at ANY time, if she has sex. Later, I discussed it with my health teacher and she told me that what the “expert” probably meant was that it was impossible to know what part of your cycle you were actually on.

I’m sure there are many studies. Here is a chart from the Centers for Disease Control that puts the effectiveness of fertility based methods at 76% (24% failure rate).

Better than 40% for sure, but overall one of the least effective methods to avoid pregnancy.

Sympto-thermal NFP methods have about 99.4% perfect-use reliability…and that’s from wiki, though they do cite solid studies.

(Scroll down to the comparison chart.)


As stated above in my prior post, curated charts do not give the method effectiveness for any of the scientific methods of natural family planning. The chart you posted includes an unspecified manner if averaging abstaining, using condoms on fertile days (!) and calendar based rhythm (!!).

NOT an accurate representation of the effectiveness of Sympto-Thermal, Billings, Marquette, or Creighton.

One very important factor to keep in mind when discussing any form of pregnancy prevention is how easy is it for people to use effectively.

A method may have a 99% pregnancy prevention when used perfectly 100% of the time, but it may be very difficult to use perfectly by some or most people.

I appreciate all your replies and posts. I feel like I have a better handle on the question now.

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