Birth control

Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent unintended pregnancy.^[1] Birth control has been used since ancient times, but effective and safe methods of birth control only became available in the 20th century.^[2] Planning, making available, and using human birth control is called family planning.^[3][4] Some cultures limit or discourage access to birth control because they consider it to be morally, religiously, or politically undesirable.^[2]

The World Health Organization and United States Centers for Disease Control and Prevention provide guidance on the safety of birth control methods among women with specific medical conditions.^[5][6] The most effective methods of birth control are sterilization by means of vasectomy in males and tubal ligation in females, intrauterine devices (IUDs), and implantable birth control.^[7] This is followed by a number of hormone-based methods including oral pills, patches, vaginal rings, and injections.^[7] Less effective methods include physical barriers such as condoms, diaphragms and birth control sponges and fertility awareness methods.^[7] The least effective methods are spermicides and withdrawal by the male before ejaculation.^[7] Sterilization, while highly effective, is not usually reversible; all other methods are reversible, most immediately upon stopping them.^[7] Safe sex practices, such as with the use of male or female condoms, can also help prevent sexually transmitted infections.^[8] Other methods of birth control do not protect against sexually transmitted infections.^[9] Emergency birth control can prevent pregnancy if taken within 72 to 120 hours after unprotected sex.^[10][11] Some argue not having sex is also a form of birth control, but abstinence-only sex education may increase teenage pregnancies if offered without birth control education, due to non-compliance.^[12][13]

In teenagers, pregnancies are at greater risk of poor outcomes.^[14] Comprehensive sex education and access to birth control decreases the rate of unintended pregnancies in this age group.^[14][15] While all forms of birth control can generally be used by young people,^[16] long-acting reversible birth control such as implants, IUDs, or vaginal rings are more successful in reducing rates of teenage pregnancy.^[15] After the delivery of a child, a woman who is not exclusively breastfeeding may become pregnant again after as few as four to six weeks.^[16] Some methods of birth control can be started immediately following the birth, while others require a delay of up to six months.^[16] In women who are breastfeeding, progestin-only methods are preferred over combined oral birth control pills.^[16] In women who have reached menopause, it is recommended that birth control be continued for one year after the last menstrual period.^[16]

About 222 million women who want to avoid pregnancy in developing countries are not using a modern birth control method.^[17][18] Birth control use in developing countries has decreased the number of deaths during or around the time of pregnancy by 40% (about 270,000 deaths prevented in 2008) and could prevent 70% if the full demand for birth control were met.^[19][20] By lengthening the time between pregnancies, birth control can improve adult women's delivery outcomes and the survival of their children.^[19] In the developing world, women's earnings, assets, and weight, as well as their children's schooling and health, all improve with greater access to birth control.^[21] Birth control increases economic growth because of fewer dependent children, more women participating in the workforce, and/or less use of scarce resources.^[21][22]