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Contraception health centre

The Pill: Contraceptive pills

The contraceptive pill is a common method of contraception using hormones to help prevent pregnancy.

Different types of the contraceptive pill include the combined oral contraceptive (the Pill) and the progestogen-only pill (POP, ‘mini-pill’).

These can be up to 99% effective in preventing pregnancy.

However, unlike condoms, the contraceptive pill does not protect against sexually transmitted infections (STIs).

Contraceptive pills are only available with a doctor's prescription, but are free for most women in the UK.

If a pill is missed, additional methods of contraception, such as condoms, may be needed depending on the type of contraceptive pill. Always follow the instructions that come with the packet.

The combined pill

The combined pill is a hormonal contraceptive containing a small amount of synthetic oestrogen and progestogen hormones. These hormones work to inhibit the body's natural cyclical hormones to prevent pregnancy. Pregnancy is prevented by a combination of factors. The combined pill usually stops the body from releasing an egg from the ovary. It also changes the cervical mucus to make it difficult for the sperm to find an egg. It can also prevent pregnancy by making the lining of the womb inhospitable for implantation.

The combined pill can be started at any stage in the menstrual cycle. If started on the first day of a period, a woman is protected against pregnancy straight away. For many women starting the combined pill up to and including the fifth day of her period will also provide immediate protection. However, always discuss how to start taking the pill with the healthcare professional prescribing it.

Progestogen-only pill

These are pills that contain only one hormone (progestogen). They do not contain oestrogen and may therefore be prescribed to women who are breastfeeding or who experience nausea with oestrogen.

Progestogen-only pills work by thickening the cervical mucus so the sperm cannot reach the egg. The hormone in the pills also changes the lining of the uterus so that implantation of a fertilised egg is much less likely to occur. In some cases progestogen-only pills stop ovulation (the release of an egg). One pill is taken every day within a specific three-hour time slot.

The progestogen-only pill is taken daily at the same time each day, with no break between packets of pills.

Are there side-effects associated with contraceptive pills?

Yes, although the majority are not serious. They include:

  • Nausea
  • Sore or swollen breasts
  • Small amount of blood, called spotting, between periods
  • Lighter periods
  • Mood changes

The following side effects are less common but more serious. If you experience any of these, seek medical advice immediately or, if this is not possible, go to a hospital A&E department for evaluation. These symptoms may indicate a serious disorder, such as liver disease, gallbladder disease, stroke, blood clots, high blood pressure or heart disease. They include:

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