There are two main risks associated with having sex without a condom. When sex is between a man and a woman, pregnancy is a very real possibility. In all cases, engaging in sex without a condom increases the risk of contracting a sexually transmitted disease (STD). Condoms do not offer perfect protection against STD infection, but the protection that they do offer ranges from good to excellent, depending on the disease in question. The risk of contracting an STD is always higher when engaging in sex without a condom.
Condoms are, first and foremost, a form of birth control, and sex without a condom or other form of birth control can often lead to pregnancy. When latex condoms are used correctly and consistently, they are very effective in preventing conception. A typical healthy couple that engages in sexual relations on a reasonably regular basis has, on average, a 20% chance of conceiving every month, resulting in nearly a 100% chance of conception during the course of a whole year. When a couple uses condoms correctly and consistently, the chance of conception is 2% to 3%, which is a very significant decrease.
The other major risk of sex without a condom is the possibility of STD infection. Over a dozen different infections can be transmitted through sexual contact. Condom use aids in the prevention of all types of STD but is most effective in preventing the spread of HIV/AIDS. HIV is a very fragile virus and normally spreads only when a bodily fluid containing the virus gains entry into a new host, generally through breaks in the skin or contact with mucous membranes. Correct condom use is highly effective in preventing this variety of transmission.
Other varieties of STD are more robust than HIV/AIDS and are able to infect new hosts more easily. The herpes simplex virus can infect a new host simply through skin contact, as can the virus that causes genital warts. Sex without a condom increases the probability that such infections will be transmitted because more skin is exposed, increasing the odds of infection being transmitted. Condom use is not, however, entirely effective in preventing the transmission of this sort of STD.
Male condoms are generally more effective in preventing the spread of STDs, as they offer a better barrier against the transmission of bodily fluids and infection than do female condoms. Female condoms, however, are highly effective in preventing pregnancy. Both types of condom can break, most often when used incorrectly, but this risk is small, and the risks associated with having sex without a condom are much greater and more serious.