Progestogen Only Pill

How effective?

99% effective if taken according to instructions. One woman in 100 will get pregnant in a year.

How it works

Contains progestogen which thickens the cervical mucus to prevent fertilisation and thins the lining of the uterus to prevent an egg implanting. In some women it stops ovulation.

Advantages

Few serious side effects. Can be used if you are breast feeding. If you are more than 3 hours late (12 hours if you are taking the POP Cerazette). Can be used by women who cannot use oestrogen. Can be used by women over 35 who smoke. Normal level of fertility returns on cessation.

Disadvantages

May be temporary minor side effects. Periods may be irregular with some bleeding in between or be missed. A small increased risk of ectopic pregnancy if it fails. May be less effective in women who weigh over 70kg.

Comments

It needs to be taken at same time each day. Not effective if taken over three hours late or after vomiting or diarrhoea. Some medicines may make it less effective but most antibiotics do not affect POPs.