What Is Sexual Activity?
Some couples think they are practicing abstinence, while participating in variety of sexual activities. Although many people have different definitions as to what is considered “sex,” some of these activities can still result in pregnancy, and almost all can result in sexually transmitted disease.
Limited information is available on young people’s ideas of what is meant by “sexual activity.” For example, among undergraduate students surveyed at a Midwestern university, 59% did not believe that oral sex would qualify as sex and only 19% thought the same about anal sex. Females (62%) were more likely than males (56%) to assert that oral sex was not really “sex.” 
Except for pregnancy, oral sex carries many of the dangers posed by standard intercourse. STDs that can be transmitted orally include human papillomavirus (HPV), herpes simplex virus and hepatitis B, gonorrhea, syphilis, chlamydia and chancroid, and possibly HIV/AIDS. 
The anus is a delicate area, and skin in the anal region can tear easily. Bodily fluids, including blood and semen, can enter the body through tiny cuts in the anus, increasing the risk of HIV. While most people are aware of the risk of contracting HIV/AIDS and hepatitis B and C through anal sex, many don’t know that you can contract a number of STDs through this behavior including herpes, gonorrhea, HPV, and chlamydia.
Despite much misinformation to the contrary, you can get pregnant from anal sex. The anal opening leads to the rectum, which is part of the large intestine, a part of the gastrointestinal (GI) tract. The GI system is not directly connected with the reproductive tract, thus sperm entering the anus cannot swim through the GI tract to reach the egg. However, semen can and does drip from the anus after ejaculation. This semen comes in contact with the vaginal opening, which is lubricated with slippery mucus. During certain times of the month, vaginal mucus acts as a conduit to usher sperm into the vagina and uterus, ultimately to a waiting egg. So, anal sex should not be considered “safe” as it puts couples at risk of both STDs and pregnancy.
Condoms are often recommened as safer sex option for couples practicing anal sex. However, condoms are more likely to break during anal sex than during vaginal sex. Thus, even with a condom, anal sex can be risky. 
Withdrawal is accomplished when, during intercourse, the man pulls out his penis just before ejaculation. This requires much discipline. As orgasm is impending, a man may not withdraw in enough time to prevent semen from escaping into the vagina. Every year one in five users of this method gets pregnant.
Withdrawal is most popular among teens, the age group for which this method is also least effective. Withdrawal requires self-control and practice, which teens are generally lacking, resulting in an increased failure rate. Furthermore this method offers little protection from STDs. Lubricating fluids escape long before ejaculation; usually they contain no sperm but can transmit diseases like the AIDS virus. 
In a study of high school students in Los Angeles, while almost half claimed never to have had sexual intercourse, almost 30% were “making love” using other methods, primarily heavy petting with mutual masturbation. 
Outercourse, or mutual masturbation, is less likely to spread STDs or cause pregnancy. However, if semen gets anywhere near the vagina, the sperm can swim into the uterus, using the vaginal mucus as a conduit. That means if semen gets on someone’s hands, and those hands get anywhere near the vagina, a pregnancy and/or STD can result.
Sometimes young couples end up having a sort of sex, but with their clothes on. The risk of pregnancy and STD is dependent on how many layers of clothes are between the two parties. Sperm will swim right through a pair of underwear, which is why you will never find a condom made of cotton.
Furthermore, in time, outercourse usually leads to intercourse, which entails all the risks discussed above.
 Sanders SA and Reinisch JM, Would you say you “had sex” if…?, Journal of the American Medical Association, 1999, 281(3):275-277.
 Lisa Remez, Oral Sex Among Adolescents: Is It Sex or Is It Abstinence? Family Planning Perspectives, Volume 32, Number 6, November/December 2000.
 Centers for Disease Control & Prevention, National Center for HIV, STD, and TB Prevention, “Can I get HIV from anal sex?” December 20, 2002 http://www.cdc.gov/hiv/pubs/faq/faq22.htm
 Williams MT, Contraceptive Information Resource, www.contracept.org, accessed 12/06.
 Schuster MA, Bell RM, Kanouse DE. The sexual practices of adolescent virgins: genital sexual activities of high school students who have never had vaginal intercourse. Am J Public Health 1997;86:1570-1576.