Vaginal bleeding after sex can have various causes.

Medical conditions that affect the vagina itself can cause this type of bleeding. They include the following:

1. Genitourinary syndrome of menopause (GSM) — This condition involves thinning, drying and inflammation of the vaginal walls after menopause. It used to be called vaginal atrophy.
2. Vaginal precancer or cancer — This is precancer or cancer that starts in the vagina. Precancer refers to irregular cells that might, but do not always, become cancerous.
3. Vaginitis — This is inflammation of the vagina that may be due to GSM or an infection.

Vaginal bleeding after sex also can be caused by conditions that affect the lower, narrow end of the uterus, called the cervix. These include:

1. Cervical precancer or cancer — This is precancer or cancer that starts in the cervix.
2. Cervical ectropion — With this condition, the inner lining of the cervix protrudes through the cervical opening and grows on the vaginal part of the cervix.
3. Cervical polyps — These growths on the cervix are not cancer. You might hear them called benign growths.
4. Cervicitis — This condition involves a type of swelling called inflammation that affects the cervix and often is due to an infection.

Other conditions that can cause vaginal bleeding after sex include:

1. Endometrial precancer or cancer — This is precancer or cancer that starts in the uterus.
2. Genital sores — These can form due to sexually transmitted infections such as genital herpes or syphilis.
3. Pelvic inflammatory disease (PID) — This is an infection of the uterus, fallopian tubes or ovaries.
4. Vulvar precancer or cancer — This is a type of precancer or cancer that starts in the outer part of the female genitals.
5. Vulvar or genital diseases — These include conditions such as lichen sclerosus and lichen simplex chronicus.

Vaginal bleeding after sex also can happen for reasons including:

1. Friction during sex due to not enough lubrication or foreplay.
2. Hormonal types of birth control, which can cause changes in bleeding patterns.
3. Bleeding during sex due to noncancerous polyps or fibroids that involve the lining of the uterus, also called the endometrium.
4. Intrauterine devices for birth control that are not placed correctly.
5. Trauma from injury or sexual abuse.

Sometimes, health care professionals find no clear cause of vaginal bleeding after sex.