Progestogen-only pill

The progestogen-only contraceptive pill is taken by women to prevent pregnancy.

It contains progestogen, a synthetic (artificial) version of the hormone progesterone that women produce naturally in their ovaries.

The progestogen-only pill differs from the combined contraceptive pill, which contains both female sex hormones oestrogen and progestogen. This makes the progestogen-only pill an option for women who cannot take the combined contraceptive pill, such as those over the age of 35 or those who smoke.

One pack of the progestogen-only pill contains 28 pills. One pill is taken every day of the menstrual cycle.

How effective is it?

When taken correctly, the progestogen-only pill is over 99% effective at preventing pregnancy. This means that less than one woman in every 100 will get pregnant in a year.

How the progestogen-only pill works

The progestogen-only pill works in two ways:

• it thickens the mucus in the neck of the womb, so it is harder for sperm to penetrate into the womb and reach an egg
• it thins the lining of the womb, so there is less chance of a fertilised egg implanting into the womb and being able to grow

Sometimes, the progestogen-only pill may also prevent ovulation (the release of an egg from your ovaries each month).

Types of progestogen-only pill

There are two different types of progestogen-only pill, which must be taken at different times of the day:

• The three-hour progestogen-only pill - must be taken within three hours of the same time each day. Examples are Femulen, Micronor, Norgeston and Noriday.
• The 12-hour progestogen-only pill (Cerazette) - must be taken within 12 hours of the same time each day. It is less commonly used than the three-hour pill.