How effective is Alesse?

Alesse is over 97 percent effective at preventing pregnancy when taken as directed. To be taken as directed, you should take the pill every day. When taken correctly, a 97 percent effectiveness rate means that if 100 women take Alesse correctly for a year while being sexually active, three will get pregnant yearly. 

This makes Alesse a very effective method of birth control. As a baseline, 60 to 85 women out of 200 will become pregnant in a year if no birth control is used. Using condoms, between two and 12 women out of 100 will become pregnant in a year. A combination estrogen-progestin oral contraceptive like Alesse, provided it contains at least 20 micrograms of estrogen, will only result in up to three women becoming pregnant, making it an efficient choice. 

It is also important to remember that Alesse takes up to seven days to work. Like other combined estrogen-progestin oral contraceptives (COCs), it can take about a week to take effect when taken correctly. Using a backup method of birth control, such as condoms, for two weeks after taking the pill is advisable to be protected from pregnancy.