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Causes
By Mayo Clinic staffVaginal bleeding during pregnancy has many causes. Some are serious, and some aren't.
First trimester
Possible causes of vaginal bleeding during the first trimester, listed in alphabetical order, include:
- Cervical cancer
- Cervical changes, including more blood flow to the cervix and softening of the cervix, which may result in harmless vaginal bleeding after sex or a pelvic exam
- Ectopic pregnancy
- Implantation bleeding: Normal in early pregnancy? (which occurs about 10 to 14 days after fertilization when the fertilized egg attaches to the lining of the uterus)
- Miscarriage
- Molar pregnancy (a rare occurrence in which an abnormal mass — instead of a baby — forms inside the uterus after fertilization)
- Some cervical infections
Second or third trimester
Possible causes of vaginal bleeding during the second or third trimester, listed in alphabetical order, include:
- Miscarriage
- Placenta previa
- Placental abruption
- Premature opening of the cervix (cervical insufficiency), which can lead to preterm birth
- Preterm labor, which may result in light bleeding — especially when accompanied by regular contractions, dull backache or pelvic pressure
- Problems with the cervix, such as a cervical infection, inflamed cervix or growths on the cervix
- Uterine rupture, a rare but life-threatening occurrence in which the uterus tears open along the scar line from a prior C-section
Normal vaginal bleeding near the end of pregnancy
In addition to potentially worrisome causes of bleeding, some vaginal bleeding near the end of pregnancy is normal. As the cervix begins to thin out and relax in preparation for labor, the thick plug of mucus that seals the opening of the cervix is dislodged. When this happens, you might notice a thick or stringy discharge that may be tinged with blood. This "bloody show" is a normal sign of impending labor that can occur up to a week or two before delivery.
Causes shown here are commonly associated with this symptom. Work with your doctor or other health care professional for an accurate diagnosis.
- Norwitz ER, et al. Overview of the etiology and evaluation of vaginal bleeding in pregnant women. http://www.uptodate.com/home/index.html. Accessed Dec. 28, 2010.
- Garner EI. Gestational trophoblastic disease: Management of hydatidiform mole. http://www.uptodate.com/home/index.html. Accessed Dec. 28, 2010.
- Lockwood CJ. Pathogenesis of spontaneous preterm birth. http://www.uptodate.com/home/index.html. Accessed Dec. 28, 2010.
- Bleeding during pregnancy. American Congress of Obstetricians and Gynecologists. http://www.acog.org/publications/patient_education/bp038.cfm. Accessed Dec. 28, 2010.
- Harms RW (expert opinion). Mayo Clinic, Rochester, Minn. Jan. 4, 2011.
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