In the United States, almost half of all pregnancies are unintended. Several safe and highly effective methods of contraception (birth control) are available to prevent unintended pregnancy. In the United States, most women of reproductive age use birth control. Between 2006–2008, 99% of women who had ever had sexual intercourse had used at least one method of birth control.
Information about Emergency Contraception: http://www.womenshealth.gov/publications/our-publications/fact-sheet/emergency-contraception.html
Information on reproductive health care, sex education, and information: http://www.plannedparenthood.org/