Combination birth control pills, also known as the pill, are oral contraceptives that contain estrogen and a progestin. Combination birth control pills keep your ovaries from releasing an egg. They also cause changes in the cervical mucus and the lining of the uterus (endometrium) to keep sperm from joining the egg.

What does the combination pill do?

The pill prevents the ovaries from releasing an egg each month (ovulation). It also: thickens the mucus in the neck of the womb, so it is harder for sperm to penetrate the womb and reach an egg. thins the lining of the womb, so there is less chance of a fertilised egg implanting into the womb and being able to grow.

Are combination birth control pills better?

Combination birth control pills are 99% effective at preventing pregnancy if used correctly. However, if not taken perfectly, the combination birth control pill is only 91% effective. For maximum pregnancy prevention, make sure to take your pills at the same time daily and start new pill packs on time.