Striving4Zen

Birth control pills, or oral contraceptives (OCs), are commonly referred to as "the Pill." Among reversible birth control methods, the Pill is considered one of the most effective. A woman naturally produces two different hormones that regulate her ovulation and menstruation: estrogen and progesterone. Birth control pills contain synthetic hormones that are similar to these naturally occurring hormones. Combination pills contain an estrogen and a progestin and work in two ways:
The body is "tricked" into thinking it is pregnant. This prevents the release of an egg, or ovulation. Without an egg to be fertilized, a woman cannot become pregnant
The cervical mucus is thickened, making it difficult for sperm to travel toward the egg and fertilize it in case an egg is released.

The most recently developed combination birth control pills are referred to as "low dose," meaning that they have 0.035 mg of estrogen or less. Through the years, research has shown that the higher amounts of this hormone used in older birth control pills are not necessary to prevent pregnancy. As a result, the doses have gotten lower, but contraceptive effectiveness has stayed the same. With "perfect use," meaning that the pills are taken exactly as directed, low-dose combination pills are more than 99% effective. This means that fewer than one out of 100 women will become pregnant when they take the combination pill in a way that is consistent and correct. Since most low-dose combination pills have the same estrogen, called ethinyl estradiol, the main difference from one brand to another is the progestin.