Loestrin 20

The 21-pill pack is taken daily for 3 weeks with no pills taken for 1 week. The estrogen part of the Pill tricks your body into thinking it is pregnant so that it doesn't release an egg. The progestin prevents ovulation. Loestrin 20 also thickens your cervical mucus to stop any movement of sperm. The cervical mucus acts as a backup to prevent pregnancy even if an egg is released.

If taken correctly on a daily basis, Loestrin 20 is as much as 99% effective in preventing pregnancy, but there is still a 1% chance that you could get pregnant. Furthermore, missing a pill or taking a pill a few hours later than normal can decrease the effectiveness. Certain medications like antibiotics are also known to increase the chance of your birth control pill failing.

See Birth Control Statistics for more information on birth control pills.