Sep 15, 2026 · 17 min · 8 segments
Data-driven Science of Fertility Awareness-Based Methods (FABMs) presented by Anita L. Nelson, MD
Anita L. NelsonGuest
Now, I do want to emphasize Natural Cycles is the first and only FDA-cleared digital contraceptives.
And what we found in these studies is that when it's combined particularly with those digital measures, the Oura Ring or the others that we're going to talk about, in typical use, we can count on it being 93% effective.
Better way to say it, it has only a 7% pregnancy rate, which puts it in the same tier as birth control pills.
Other issues around this, for women who don't want exogenous hormones, this is hormone-free.
So physicians are able and clinicians of all sorts are able to write prescriptions for women to be able to use this as their method of birth control.
As I mentioned, in typical use, and that's the number we should be talking to our patients about, it's wonderful to know that if the woman took her pill every day at the same time that she'd only have a 1% pregnancy or that if he put on a condom correctly and consistently every time the failure rate would be less than 2%.
And that's where we find that the natural cycles and oral contraceptives fall into that middle tier of efficacy.
It's better than Just the barrier methods themselves, it may not be quite as good as we know about in typical use for the implant or for the IUDs.
But in the methods where the vast majority of women are finding themselves or using contraception, this belongs in that middle tier.
One other thing I want to point out is that I mentioned we've done studies over time of the typical use failure rate of the users of this method.
And what has been very nice is you can see on the bottom there, those are different dates.
What has been happening is that typical use PERL index has not gone down over time.
Maybe the users were true believers and they were going to use it perfectly.
and give you one number but as it expanded to the general population were we going to have a decrease in the efficacy but I think you can see here that as we had a growth over time that that failure rate has actually diminished and part of that is some very important changes that were improvements made in the algorithm over time because this company is always looking for ways to get even better answers for patients.
And then, of course, the introduction of the easier to use digital methods for determining basal body temperature.
Now, I do want to emphasize Natural Cycles is the first and only FDA-cleared digital contraceptives.
And what we found in these studies is that when it's combined particularly with those digital measures, the Oura Ring or the others that we're going to talk about, in typical use, we can count on it being 93% effective.
Better way to say it, it has only a 7% pregnancy rate, which puts it in the same tier as birth control pills.
Other issues around this, for women who don't want exogenous hormones, this is hormone-free.
So physicians are able and clinicians of all sorts are able to write prescriptions for women to be able to use this as their method of birth control.
As I mentioned, in typical use, and that's the number we should be talking to our patients about, it's wonderful to know that if the woman took her pill every day at the same time that she'd only have a 1% pregnancy or that if he put on a condom correctly and consistently every time the failure rate would be less than 2%.
And that's where we find that the natural cycles and oral contraceptives fall into that middle tier of efficacy.
It's better than Just the barrier methods themselves, it may not be quite as good as we know about in typical use for the implant or for the IUDs.
But in the methods where the vast majority of women are finding themselves or using contraception, this belongs in that middle tier.
One other thing I want to point out is that I mentioned we've done studies over time of the typical use failure rate of the users of this method.
And what has been very nice is you can see on the bottom there, those are different dates.
What has been happening is that typical use PERL index has not gone down over time.
Maybe the users were true believers and they were going to use it perfectly.
and give you one number but as it expanded to the general population were we going to have a decrease in the efficacy but I think you can see here that as we had a growth over time that that failure rate has actually diminished and part of that is some very important changes that were improvements made in the algorithm over time because this company is always looking for ways to get even better answers for patients.
And then, of course, the introduction of the easier to use digital methods for determining basal body temperature.
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