context: You've just finished having sex with your partner, when you look down and see blood on the sheets. You don't have your period and aren't supposed to get it anytime soon, so what gives? While vaginal bleeding after sex can be alarming, it's also fairly common -- affecting up to 9% of menstruating women -- and probably no cause for concern. But it can also be caused by an infection, and in rare cases, it's a sign of cervical cancer. The most common causes for vaginal bleeding after sex both start in the cervix, which is the narrow, tube-like end of the uterus that opens into the vagina. One of those causes is cervical inflammation, or cervicitis. It can be ongoing and totally harmless, or it can happen because of a sexually transmitted infection that you need to get treated, like chlamydia or gonorrhea. Both types of cervical inflammation can cause bleeding after sex. A second common reason for bleeding after sex are cervical polyps. They are growths that are usually small -- about 1 to 2 centimeters -- that often appear on the cervix where it connects to the vagina. Most aren't cancerous, and a doctor can remove them during an appointment. Other causes of vaginal bleeding after sex include: Friction during sex or not enough lubrication Normal uterine bleeding if you're just beginning your period or if it's just ended A cervical or vaginal infection Genital sores caused by herpes or another condition A precancerous cervical spot Cervical ectropion (when the inner lining of the cervix pokes through the cervical opening and grows on the vaginal side of the cervix) Pelvic organ prolapse (when pelvic organs, like the bladder or uterus, jut beyond the vaginal walls) Cancer of the cervix, vagina, or uterus While many of these causes don't need treatment and are harmless, sometimes vaginal bleeding after sex can be a sign of a more serious problem. If you have some minor bleeding occasionally after sex, chances are that everything is fine. But the only way to know for sure is to see your doctor for a physical exam. If the bleeding happens right before you get your period or within a few days after it ends and it doesn't happen again, you can hold off on making that appointment. You can also probably hold off if you recently had a pelvic exam and Pap smear and got a clean bill of health. In all other cases -- or if you're just worried -- it's best to get checked out to rule out infection or anything more serious. If you're postmenopausal, any bleeding after sex isn't normal. See your doctor to rule out cervical cancer, endometrial cancer, and other issues. Your doctor's first step will probably be to ask you some questions to see if there's an obvious cause for the bleeding, like breakthrough bleeding after you just start to take a birth control pill. She'll also want to know if you're having pain during sex, which can be a sign of inadequate lubrication or infection, depending on when it happens. Your doctor will give you a pelvic exam and look for any source of the bleeding, like vaginal tears or lesions, signs of pelvic organ prolapse, cervical polyps, or inflammation. If your doctor finds any polyps, she might be able to remove them in the office and send them to a lab for testing, or make a later appointment to have them surgically removed. During a Pap test, your doctor can swab your cervix to test for sexually transmitted infections like chlamydia and gonorrhea, which can cause bleeding after sex and are treated with antibiotics. The Pap test also detects any sign of abnormal, precancerous growths or cancer cells. If your Pap test reveals any abnormalities on your cervix at the time of your exam, you'll probably get a colposcopy. It starts out like a Pap test, but takes a bit longer, and the doctor will use a special magnifying device called a colposcope to get a closer look at the cervix. If your doctor sees anything suspicious, she can take a small sample of tissue for testing. If bleeding after sex is an ongoing thing, your doctor may recommend a colposcopy even if your Pap test results are normal, to get a better look at your cervix. If you're postmenopausal, your doctor might do a transvaginal ultrasound to get a closer look at the pelvic organs or an endometrial biopsy to look for abnormal cells in the endometrial tissue that lines your uterus. Vaginal bleeding after sex can be scary if you're pregnant, but it's probably not a cause for concern. Your cervix may bleed more easily during pregnancy because extra blood vessels are developing in the area. It might. A recent study found that just over half of women who had bleeding after sex reported that it cleared up on its own within 2 years. You can rule out the most innocent causes of bleeding after sex, like friction during intercourse or not enough lubrication, by simply using a lubricant before and during sex. You can also wait a bit longer after your period ends to start having sex again, if it seems like regular uterine bleeding at the tail end of menstruation is the culprit. Removing cervical polyps or treating cervical infections should also clear up post-sex bleeding, if either was the cause.