The contraceptive pill works in three main ways to prevent pregnancy:

• Prevents ovulation - Stops your ovaries from releasing an egg each month
• Thickens cervical mucus - Makes it harder for sperm to reach an egg
• Thins the womb lining - Reduces the chance of a fertilised egg implanting. The combined pill primarily works by preventing ovulation, while the mini pill mainly works by thickening cervical mucus.

There are two main types of contraceptive pills:
Combined Pill (COC)

• Contains both oestrogen and progesterone
• Usually taken for 21 days followed by a 7-day break
• Examples include Microgynon, Rigevidon, Yasmin, Cilest, and Marvelon
• Over 99% effective when taken correctly

Mini Pill (Progestogen-Only Pill/POP)

• Contains only progesterone
• Taken every day without a break
• Examples include Cerazette, Cerelle, Noriday, and Desogestrel
• Suitable for women who can't take oestrogen (e.g., breastfeeding mothers, smokers over 35)

When taken correctly (at the same time every day without missing doses), the contraceptive pill is over 99% effective at preventing pregnancy. However, with typical use (accounting for missed pills or other factors), effectiveness drops to around 91%. Effectiveness can be reduced by:

• Missing pills or taking them late
• Vomiting or severe diarrhoea within 2-3 hours of taking a pill
• Certain medications (antibiotics, anticonvulsants, St John's Wort)
• Not following the instructions correctly