Natural Family Planning

Natural family planning is a form of birth control where natural signs, such as body temperature, are used to identify when a woman is at her least and most fertile during each menstrual cycle.

  • It is helpful to be trained by an expert in this method as it can be difficult to monitor.
  • Natural Family Planning can be difficult for young people as it relies very much on having a regular menstrual cycle.
  • This method doesn’t prevent Sexually Transmitted Infections (STIs).

How It Works

Consult your GP to establish the method that suits you best. 

The Calendar Method

  • Record the first day of every period (day one of each menstrual cycle) for six months.
  • Work out the length of each menstrual cycle during those six months. This is the number of days from the first day of your period to the first day of your next period (normally about 28 days).
  • Take the length of your shortest cycle and the length of your longest cycle.
  • Subtract 18 days from the length of your shortest cycle – this is the first day of your fertile period.
  • Subtract 11 days from your longest cycle – this is the last day of your fertile period.
  • Do not have sex from the first day to the last day of your fertile period.

The Temperature Method

  • Every morning, take your temperature (using a thermometer) after waking, before you get out of bed. Try and take it the same time each morning. Keep a record of these readings.
  • After six readings, work out your average body temperature (add the measurements and divide by six).
  • When you take three temperatures in a row that are all higher than your average, ovulation has taken place.
  • From the third day of increased temperature (the third day after ovulation), you will have entered an infertile phase because it is unlikely that your egg will be fertilised. You will be protected against pregnancy from this time until your next fertile period.

However, various factors can upset your body temperature, such as illness or some medications.

The Mucus Method

  • Every morning, use your finger to take a sample of the secretion coming out of your vagina.
  • Press the sample against your thumb and slowly separate your thumb and finger, to test the consistency.
  • If it seems clear and stringy, like egg white, you are about to ovulate.
  • You will enter an infertile phase from four days after this point (when there is no longer lots of clear mucus), which lasts until your next fertile period.

However, if you have recently had sex or are sexually aroused, the consistency of your secretion will be affected. A vaginal infection such as thrush will also affect your secretion. Therefore this is not a particularly effective method of contraception when used alone. For more information, speak to your GP or nurse.