Hormonal Contraception: Systemic Estrogen and Progestin Preparations.

Combined hormonal contraception (CHC) are short-acting, reversible methods containing both estrogen and progestin. Available CHC methods include combined oral contraceptives, transdermal patches, and vaginal rings. The combined oral contraceptive remains the most commonly used contraceptive method in the United States. The general principles of CHC will be reviewed, including mechanism of action and effectiveness. Unless otherwise stated, these principles apply to all CHCs. When discussing clinical studies and specific considerations related only to pills, patches, or rings, the method(s) will be specified. Words that specify sex are used when discussing studies in which sex was specified.