How it works
You can only get pregnant on a few days in each cycle, around ovulation, plus the days before when sperm can survive. By recording one or more fertility signs every day, you identify those days and avoid unprotected sex then.
People who want a method without hormones or devices and are able to track their cycle carefully every day.
How effective is it?
Typical use
77%
In real life about 23 in 100 people get pregnant in a year with typical use.
Perfect use
95%
About 5 in 100 when used exactly as directed every time.
2 to 23 in 100 with typical use, depending on the method and how consistently it is followed
See how it ranks against every method in the effectiveness chart.
How to use it
Learn the method from a trained fertility awareness teacher if possible; it usually takes 3 to 6 cycles to learn to read your signs reliably.
Choose a method: temperature (checking your resting temperature each morning), cervical mucus (noticing changes in vaginal secretions), calendar (counting cycle days), or symptothermal (combining several signs, which is the most reliable).
Record your signs every day, on paper or in an app, and follow the rules for your method about which days are fertile.
On fertile days, avoid vaginal sex or use a condom or other barrier method.
Get advice again after childbirth, while breastfeeding, coming off hormonal contraception or approaching menopause, as signs change.
Pros and cons
Advantages
- No hormones, devices or side effects
- Low cost once learned
- Helps you understand your own cycle
- Acceptable to people with religious or cultural concerns about other methods
- Can also be used to plan a pregnancy
Disadvantages
- Less effective than most methods with typical use
- Needs daily tracking, commitment and usually a cooperative partner
- Takes several cycles to learn properly
- Illness, stress, travel, shift work and alcohol can affect signs
- Does not protect against STIs
Effect on periods: No effect on periods; it relies on tracking your natural cycle.
Possible side effects
- No physical side effects
- Some people find the daily tracking and periods of abstinence stressful
- Pregnancy risk if fertile days are misjudged, especially while learning
Who it may not suit
A clinician checks your medical history before you start. This list is not complete.
May not be suitable if
- Your cycles are very irregular
- You have recently given birth, are breastfeeding, have recently stopped hormonal contraception or are near menopause
- A pregnancy would be very risky for your health
- You or your partner may find it hard to avoid sex or use a barrier on fertile days
Get medical help if
- Your period is late or you think you may be pregnant
- You had unprotected sex on a fertile day and want emergency contraception
- Your cycles suddenly become irregular or you notice unusual bleeding
Frequently asked questions
How effective is natural family planning?
It depends heavily on the method and how carefully it is followed. With typical use, between 2 and 23 in 100 people get pregnant in a year; methods combining several signs, such as the symptothermal method, tend to do better than calendar counting alone.
Is the rhythm method the same as fertility awareness?
The rhythm or calendar method is one type of fertility awareness that relies only on counting cycle days. It is generally less reliable than methods that also track temperature and cervical mucus.
Can I use a period-tracking app as contraception?
Most period-tracking apps are not designed as contraception. A few apps have been cleared by regulators for this use, but they still depend on accurate daily data and on avoiding sex or using a barrier on fertile days.
How long does it take to learn fertility awareness?
Most people need around 3 to 6 cycles to learn to recognize their signs reliably. Learning from a trained teacher is recommended, and another method such as condoms should be used while learning.
Can I use fertility awareness if my periods are irregular?
It is harder and less reliable with irregular cycles, especially calendar-based methods. Talk to a clinician or fertility awareness teacher about whether it suits you.
Sources
Reviewed 1 November 2026. We link to the guidance itself so you can check it.