The Combined Pill

The popular form of contraception which many British women refer to simply as the 'the pill', has a more scientific name: the combined oral contraceptive pill. The word 'combined' refers to the combination in the pill of two female hormones: oestrogen and progesterone. The presence of both hormones makes the combined pill different to the progesterone-only contraceptive pill, which, obviously enough, contains only progesterone. There are a variety of reasons why women use the combined contraceptive pill and not all are related to preventing pregnancy. The hormones in this pill help to regulate unpredictable periods, relieve symptoms of PMS and manage endometriosis - a medical condition which can cause painful periods. The combined pill is not suitable for everyone - some women are advised not to introduce additional oestrogen into their bodies. If you are considering taking the pill, you will need to go and see your doctor to get advice and a prescription. Your doctor will help you decide which contraceptive pill is best for you. But first, it's useful to know how the combined oral pill stops you getting pregnant...

How It Works

The combined oral contraceptive pill comes in different forms - some brands are taken every day and some for only three weeks a month. Others contain the same amounts of hormone in each pill whereas some vary the amount of hormones you receive as the cycle progresses. The contraceptive mechanism of your pill will depend on the type of pill you choose. There are, however, three basic ways in which the pill prevents pregnancy...

Preventing ovulation - the oestrogen and progesterone in the combined pill actually stop your ovaries producing and releasing eggs - which means that if you have sex, there are no eggs for your partner's sperm to fertilise. The hormones in the pill suppress the release of other sex hormones that are necessary for ovulation. During each menstrual cycle, if you don't take the pill, a part of your brain called the hypothalamus triggers the release of follicle-stimulating hormone, which makes the follicles in your ovaries produce eggs. Later, the hypothalamus initiates the release of luteinising hormone, which causes one ovary to release a mature egg. This egg then travels down your fallopian tube, where it may be fertilised, and then into your uterus (from here the egg will be flushed out during your period if it isn't fertilised). This egg development and release process is 'shut down' by the combined pill.

Thickening cervical mucus - the hormones in the combined pill can actually help block sperm cells' access to the uterus and fallopian tubes. This helps prevent pregnancy in the unlikely event that an egg has actually been released while taking the pill. The sperm cells' path to the uterus is blocked by mucus at the mouth of the uterus (called the cervix). The hormones in the pill reduce the amount of this mucus but make it much thicker and more difficult for the sperm to penetrate.

Thinning uterus lining - each menstrual cycle that you are not on the pill, the lining of your uterus thickens as ovulation approaches, and gets ready to receive and nurture a fertilised egg. The hormones in the pill prevent the lining of your uterus becoming thick, therefore, in the unlikely event of an egg being fertilised, it won't be able to implant in your uterus and will not develop into a baby.

Types Of Pill

A variety of different strengths and brands of the combined pill is available in Britain. The main difference between them is that some pills are low-strength oestrogen and others are standard-strength oestrogen. Your doctor will advise you as to which is best for you.

21-Day Versus 28-Day Pills

Both low-oestrogen and standard-oestrogen pills are available in 21-day packs. This means that you take a pill for every day for 21 days and then take a seven-day break before starting a new pack. Providing that you have taken your pills correctly, you don't need to use additional contraception during those seven days. In addition to the 21-day pack, the standard-strength oestrogen pill also comes in 28-day packs. In the 28-day pack, only 21 of the pills contain active hormones which prevent pregnancy. Once these pills have been taken, you continue to take the seven non-active pills during the 'seven-day break' and then immediately move on to the next pack of pills. Some women find this method easier because they know that they have to take a pill every day.

Hear about the benefits of the birth control pill in our birth control forum.

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