Abortion: The premature ending of a pregnancy, either spontaneous, or induced (occurring as the result of human action to end the pregnancy).

Barrier method: Barrier methods prevent pregnancy by creating an actual, physical barrier between the sperm and the egg, or prevent some sexually transmitted infections by preventing the exchange of body fluids during sexual activity. Barrier methods to prevent pregnancy include the condom, intrauterine device (IUD), diaphragm, cervical cap, and shield. Condoms reduce the risk of sexually transmitted infections, including HIV.

Birth defects: Physical problems that occur prior to birth or, sometimes, at birth; some, such as Down syndrome, are genetic; others, like fetal alcohol syndrome, are caused by environmental exposure in the uterus to harmful agents such as cigarettes, alcohol, or other drugs; some, like cerebral palsy, may be caused by injury at birth or shortly thereafter.

Combined pills: Birth control pills that contain both estrogen and progestin.

Condom: A barrier method of contraception, made of latex or polyurethane. The male condom fits over the penis; the female condom fits inside the vagina.

Contraindicated: Conditions under which a particular regimen or medication is not recommended; any condition which will make some particular line of treatment ineffective, improper, or undesirable.

Conception: The moment when the sperm enters the ovum (egg), fertilizing it, and forming a viable zygote (a healthy fertilized egg).

Dating violence: Physical, sexual, and/or emotional violence within a dating relationship; a relationship in which one partner harms the other through such actions as hitting, punching, raping, or degrading.

Depo-Provera (“depo”): An injection once every 12 weeks of a hormone, much like the progesterone a woman produces during the last two weeks of each monthly cycle; stops the woman's ovaries from releasing an egg, and prevents pregnancy.

Ectopic pregnancy: This condition occurs when the fertilized egg implants itself outside the uterus, usually in the fallopian tube, more rarely in the ovary, cervix, or abdomen; it is a life-threatening condition for the woman and a deadly condition for the embryo, since it cannot develop to full-term; medical intervention is usually necessary to save the woman's health and life.

Embryo: The stage of human development extending from after implantation until the end of the seventh or eighth week of pregnancy.

Emergency contraception: Use of the same medication as in birth control pills (either progestin-only or the Yuzpe regimen of combined hormone pills) to prevent pregnancy after unprotected sex. Also called Plan B^®, the “morning after pill,” or emergency birth control pills.

Estrogen: a hormone contained in combined oral contraception and that is much like hormones that a woman’s body produces naturally.

Fertilization: the process whereby a sperm penetrates the egg, creating a zygote (cell that contains a complete complement of human genes).

Fetus: The stage of pregnancy, from about the 8th week until birth, in which physical characteristics are first apparent.

Food & Drug Administration (FDA): the agency within the U.S. Department of Health & Human Services that is charged with ensuring the safety of commercially available products within the United States, including: food and dietary supplements; drugs, both prescription and over-the-counter; medical devices, and vaccines.

Gynecologist: a doctor specially trained to care for women and their sexual and reproductive health; may also double as an obstetrician, caring for female patients throughout pregnancy, delivery, and immediate post-delivery.

Implantation: a process whereby the fertilized egg attaches itself to the wall of the uterus, thereafter receiving all that is needed to sustain itself from the woman’s uterus; after implantation is complete, pregnancy begins.

Mifepristone (RU 486): A prescription drug that terminates a pregnancy. Also known as the “abortion pill.”

Obstetrician: a doctor specially trained to care for a pregnant woman throughout her pregnancy, delivery, and immediate post-delivery.

Ovulation: release of an egg, usually one per menstrual cycle; at release, the egg is ready for fertilization.

Pediatrician: a doctor specially trained to care for infants, children, and teens; may further specialize either in infant and child health care or in teen health care.

Plan B^®: a specially packaged levonorgestrel-only (progestin-only) formulation, for use as emergency contraception; recently approved by the Food & Drug Administration for non-prescription sale to women ages 18 and over.

Pregnancy: The time between when a fertilized egg implants in the uterus and when the woman gives birth.

Progestin-only pills: Birth control pills that contain no estrogen.

Progestin-only regimen: Emergency contraceptive regimen relying on levonorgestrel only, consisting of 1.50 mg in a single dose or 0.75 mg in two doses taken 12 hours apart.

Sexual assault: A general term that includes any unwanted sexual contact, including rape, incest, and unwanted fondling.

Sexually transmitted infectionss (STIs): Infections, either bacterial or viral, that are spread from one person to another by sexual contact.

Unintended pregnancy: Any pregnancy that is not planned; may include both wanted and unwanted pregnancies.

Unprotected sexual intercourse: Vaginal, oral, or anal sex without the use of brith control or other contraception. Vaginal sex can put a woman at risk of pregnancy through, for example, missed pills, delayed Depo-Provera injection, incorrectly used condom, forced sex, nonuse of birth control, or drug interaction; any act of sex (vaginal, oral, or anal) that is not protected puts participants at risk of pregnancy or sexually transmitted infections (STIs).

Uterus: also called the womb, the reproductive organ in the female body within which the fertilized egg implants itself and develops, receiving everything it needs from the woman’s body.

Vaginal bleeding: menstrual flow and/or menstrual spotting; any blood appearing from the vaginal opening.

Yuzpe regimen: A method of emergency contraception using combined pills; estrogen-progestin regimen, consisting of two doses, taken 12 hours apart, of 100 mcg ethinyl estradiol plus 0.50 mg of levonorgestrel.