It stops ovulation, thickens cervical mucus to prevent sperm reaching an egg and thins the lining of the uterus to prevent a fertilized egg implanting.
Advantages
99 % effective if taken according to instructions.
Usually makes periods regular, lighter and less painful.
Reduces risk of cancer of the ovary,uterus and colon and may protect against pelvic inflammatory disease.
Suitable for healthy non-smokers up to the menopause.
When you stop using the combined pill your fertility will return to normal.
Low risk of serious side-effects such as blood clots, breast and cervical cancer.
Disadvantages
Can have temporary side-effects such as headaches, nausea, mood changes and breast tenderness.
Missing pills, vomiting or severe, long-lasting diarrhoea can make it less effective.
Some medicines can make it less effective.
Break through bleeding and spotting is common in the first months.
Not suitable for very over weight women or smokers over 35 years.
