Natural family planning and fertility awareness

Fertility awareness means learning a method and following its rules about when to avoid sex or use a barrier. You cannot rely on a calendar’s estimated fertile window alone for contraception.

What you learn to observe

You record body temperature, vaginal discharge and your menstrual cycle every day. A specially trained professional teaches you how to use those observations. On days identified as fertile, the method involves avoiding sex or using condoms.

Some methods use fertility signs, such as cervical secretions or body temperature. Others use calendar calculations; CDC distinguishes between these approaches. Ask which method you are being taught, what information it needs and what to do when an observation is missing or difficult to interpret.

Learning takes practice. The NHS says it can take 2 to 3 menstrual cycles to understand how to use the method properly, with additional contraception or no sex during that time. Ask your teacher how they will check that you understand the method before you rely on it.

How effectiveness varies

The NHS says fertility awareness methods are between 91% and 99% effective when used correctly all the time. If instructions are not followed exactly, it gives 76% effectiveness: 24 in 100 women become pregnant over a year. Those figures describe groups of women using the methods. They cannot estimate your chance of pregnancy on a particular day.

US guidance presents a different range. CDC lists typical use failure rates of 2-23% across fertility awareness methods and says failure rates vary between them. These US figures describe failure rates across methods; the NHS figures above describe effectiveness. Neither can tell you whether a particular episode of sex will result in pregnancy.

Before choosing this approach, consider the daily work involved and the plan for fertile days. Ask yourself whether avoiding sex or using a barrier on those days fits your circumstances. Discuss this at your teaching appointment.

Where period apps fit

The NHS does not officially recommend apps or fertility-monitoring devices for this purpose. In the US, FDA-cleared contraceptive software exists, and CDC includes it within fertility awareness methods. This software is specifically intended for contraception. It does not mean every period-tracking app can be used in the same way.

Veya is a diary, and its estimates must never be used as contraception. A date you entered is a record; an app-generated fertile window is an estimate. For a contraceptive plan, use advice about the specific method you have been taught.

When extra advice is needed

Irregular periods can make fertility awareness unsuitable. The NHS also advises asking whether the method is suitable if you need to avoid pregnancy because of a health condition or a medicine that could affect a baby. Do not stop a prescribed medicine without talking to your doctor.

CDC notes that menstrual changes around the first periods and perimenopause can complicate these methods. Breastfeeding can also make fertility awareness less effective. Breastfeeding-based contraception, called the lactational amenorrhoea method, has its own conditions; it is a separate approach from simply tracking your cycle.

Fever can make temperature observations difficult to interpret, and some medicines affect cycle regularity or fertility signs. If this happens, discuss it with the practitioner rather than trying to adjust the method yourself. Fertility awareness does not protect against STIs; condoms can reduce that risk.

After sex without reliable contraception

Contact a pharmacist or sexual health service today (UK, US and elsewhere) about emergency contraception if you had sex without a barrier on a potentially fertile day, miscalculated the days, or relied on an app estimate. Explain what happened and when. The sooner emergency contraception is used, the more effective it usually is.

Finding someone to teach you

Book with a GP surgery, sexual health clinic or midwife in the UK and ask for someone trained in fertility awareness. In the US and elsewhere, ask your healthcare provider for a practitioner with that training. Explain whether you want to avoid pregnancy or are considering trying to conceive, and ask what contraception to use while learning.