How effective is NC° Birth Control?
What do we mean by effectiveness?
Birth control effectiveness is calculated using the Pearl Index (PI). This represents the number of unintended pregnancies that occur when a group of 100 women use a particular method of birth control for a year.
Each birth control method has two categories of Pearl Index: typical use and perfect use.
Understanding typical & perfect use
Typical use
Includes all unintended pregnancies and reflects the way a method is used in everyday life.
Perfect use
Only includes pregnancies caused by the failure of the method, and so reflects effectiveness when it’s used perfectly.
Here's an example:
A method has a typical use Pearl Index of 7 (meaning 7 women in 100 get pregnant during one year of use). When birth control effectiveness is shown as a percentage, we look at the number of pregnancies that did not happen. So in this case, 93 out of the 100 women in the group did not get pregnant. This means the method is 93% effective with typical use.
How do birth control methods compare?
Non-hormonal
Natural Cycles°
93%
Typical Use
Includes all unintended pregnancies, such as due to having unprotected sex or using withdrawal on a Red Day, as well as pregnancies that occur while the method is used as intended
98%
Perfect Use
Only includes pregnancies due to condoms breaking, or the app giving a wrong Green Day
Select other methods to compare
Hormonal
Contraceptive Pill
93%
Typical Use
Includes pregnancies due to a woman forgetting to take the pill, or taking it at the wrong time.
>99%
Perfect Use
Only includes pregnancies while using the pill exactly as specified by the manufacturer.
Percentage of typical/perfect users who did not get pregnant with the method over one year of use. Reference: Contraceptive Technology (Table 26 - 1). 21st Edition, 2018
How does NC° Birth Control calculate its effectiveness?
As a regulated medical device, we follow rigorous processes to protect our users and we are constantly monitoring our Pearl Index. Our FDA clearance is based on the study of more than 15,000 women. The study looked at all possible reasons women become pregnant, including condoms failing and the app giving an incorrect green day.
NC° Birth Control Pearl Index
Out of 100 women over 1 year of use
7on average got pregnant in total
5from unprotected sex on red days
2despite using a condom or abstaining on red days
0.5from the app giving a wrong green day
Discover Natural Cycles° today
Some common questions we get asked about effectiveness
NC° Birth Control is more than an app. It’s a certified medical device that’s regulated by official bodies. And while apps can get a bad rep when it comes to data privacy, one of the reasons we charge a subscription fee is to protect our users. We take your data privacy very seriously and will never monetize your data by selling it to third parties.
No, the method is just as effective! Changes in your sleep pattern, or forgetting to measure doesn’t affect how effective NC° Birth Control is at preventing pregnancy. However, if the app doesn’t have enough data due to poor sleep or forgetting to measure, you might get more red days (when you’ll need to abstain from sex or use protection).
It’s actually different in a couple of ways! Compared to manual charting, the Natural Cycles algorithm avoids some of the human error that can happen, since it does the work for you. It also takes historical temperature and cycle data into account. Compared to calendar-based methods (such as the rhythm method) Natural Cycles provides greater accuracy in finding your personal fertile window because it's individualized to your ovulation. This puts NC° Birth Control in a higher effectiveness category than the rhythm method and other methods that assume a set cycle pattern.
As a regulated medical device, Natural Cycles is subject to rigorous testing and yearly audits. Our FDA clearance is based on the analysis of more than 15,000 women over 180,000 cycles. We are constantly monitoring the app’s performance to ensure our Pearl Index remains constant and our effectiveness rate remains the same. You can read more about our research, including our effectiveness studies, here.
Yes. The effectiveness of NC° Birth Control does not change for those with different cycle lengths or patterns. However, irregular cycles and ovulation means that the algorithm needs to give more red (fertile) days before ovulation in the event that it would happen earlier than expected. If you have very irregular cycles or PCOS, you should therefore expect to have less green (non-fertile) days and more days where you need to use protection.
The NC° app is cleared by the FDA to be used with NC° Band, Oura Ring, and Apple Watch — all compatible devices meet our strict effectiveness standards. NC° Birth Control is 93% effective with typical use and 98% effective with perfect use.