Vaginal Sex

Vaginal sex (also called vaginal intercourse or coitus) involves the insertion of the male sex organ (penis) into the female sex organ (vagina). Vaginal intercourse is the usual method for producing offspring in organisms that reproduce sexually, including humans.

In people who have sexual relationships with members of the opposite gender (i.e., heterosexuals), vaginal sex is the most common type of sexual intercourse. Other types of vaginal sex include cunnilingus (oral sex performed on a woman), vagina-to-vagina sex (in women who have sex with women [WSW]), finger(s)-to-vagina sex (also called digital stimulation), and vaginal sex involving sex toys (e.g., vibrators, dildos).

Couples who engage in vaginal sex should be sure to practice safer sex. Sexually transmitted diseases (STDs), including HIV/AIDS, can be spread through this sexual activity. According to the Centers for Disease Control and Prevention (CDC), sexual intercourse is the most common method of HIV transmission in many parts of the world.

The only way to avoid pregnancy and prevent the spread of STDs (e.g., genital herpes, genital warts, HIV) with certainty is to refrain from having sexual intercourse (called abstinence).

The safest sex is between uninfected people who have never had another sexual partner. Before having vaginal sex, partners should be honest with each other about their sexual and medical history.

To reduce the risk for STDs and help avoid pregnancy, a latex condom with a water-based lubricant (e.g., KY Jelly®) should be used for sexual intercourse. Condoms reduce the risk for STD transmission and for pregnancy, but they are not 100% effective. Safer vaginal sex also involves using other forms of contraception (e.g., birth control pills) if pregnancy is not desired.

Many heterosexual couples consider vaginal intercourse to be the most intimate, pleasurable, and satisfying sexual behavior. Other types of sexual activity (e.g., deep kissing, manual stimulation, oral sex) often are considered foreplay—sexual behavior that occurs prior to and leads up to sexual intercourse.

The structure of the male and female reproductive organs (genitals) and the sexual response cycle make vaginal intercourse possible. When a male becomes sexually aroused (stimulated), tissues in the penis become filled with blood causing the organ to become stiff and hard. This process, which is called an erection, allows the man's penis to penetrate the woman's vagina. When a woman becomes sexually aroused, the vagina becomes lubricated to make this penetration easier.

Couples can have vaginal intercourse in several different positions. Common positions include either the man or the woman lying on top of and facing his or her partner. This position may add to the intimacy of sexual intercourse.

During sex, the couple usually moves in a way that causes the penis to slide in and out within the vagina, resulting in sensations that are pleasing to both the man and the woman. These sensations often lead to male ejaculation (ejection of semen from the penis) and also may lead to male and female orgasm (sexual response characterized by the release of sexual tension).

When a sexually mature man and a sexually mature woman have vaginal sex, a male sex cell (sperm) may unite with a female sex cell (egg) and result in pregnancy. In some cases, pregnancy can occur even if the man does not ejaculate inside the woman's vagina. For example, ejaculation that occurs close enough to the vaginal opening may allow semen to enter the vagina and result in pregnancy.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 06 Dec 2008

Last Modified: 05 Oct 2011