The COC contains synthetic versions of the naturally occurring hormones oestrogen and progesterone which prevent an egg from being fertilised in three different ways:-

• By stopping the ovaries from releasing the egg (ovulating)
• Thickening the mucus in the neck of the womb which makes it more difficult for the sperm to reach the egg.
• Thinning the lining of the womb which make it difficult for the egg to implant itself

The combined pill is taken for 21 days in a row followed by a seven day pill-free break. This break allows the lining of the womb which has built up over the month to break down just as in a normal period. The patient then continues with the next 21 days of tablets. For people who find they have difficulties remembering to stop and restart the pill there are products available which contain 28 tablets where one tablet is taken every single day. Seven of these tablets are inactive, containing no hormones, so this is the same as stopping the tablets for seven days.

The pill must be taken correctly to ensure that it is effective; here are some of the golden rules:-

• The combined pill should be taken at a similar time each day so that a routine is built up, helping to remember to take the tablet
• Each packet displays the days of the week and each combined pill should be taken on the corresponding day
• The effectiveness of the combine pill can be reduced if the patient suffers from sever vomiting or diarrhoea
• Certain medications can interact with the combined pill and reduce its efficacy such as antibiotics, epilepsy drugs and St John's Wort

• Reducing the risk of ovarian cancer
• Reducing premenstrual syndrome symptoms
• Reducing acne symptoms (although not effective for everyone)
• Reducing bleeding, making periods lighter and less painful

There are some disadvantages to the combined pill:-

• Can cause some temporary side effects such as headaches, nausea, mood swings and breast tenderness
• Can increase blood pressure
• Does not protect against sexually transmitted infections
• Can increase the risk of certain conditions such as thrombosis (blood clots) and breast cancer

Due to the oestrogen content, the combined pill is not recommended for certain groups of patients:-

• Women over 35 who smoke
• Patients who are very overweight
• Those suffering from thrombosis (blood clots), high blood pressure, heart disease, severe migraines or breast cancer