Causes

By Mayo Clinic Staff

Vaginal bleeding during pregnancy has many causes. Some are serious, and many aren't.

1st trimester

Possible causes of vaginal bleeding during the first trimester include:

  1. Ectopic pregnancy (in which the fertilized egg implants and grows outside of the uterus, such as in a fallopian tube)
  2. Implantation bleeding (which occurs about 10 to 14 days after conception when the fertilized egg implants in the lining of the uterus)
  3. Miscarriage (the spontaneous loss of pregnancy before the 20th week)
  4. Molar pregnancy (a rare occurrence in which an abnormal fertilized egg develops into abnormal tissue instead of a baby)
  5. Problems with the cervix, such as a cervical infection, inflamed cervix or growths on the cervix

2nd or 3rd trimester

Possible causes of vaginal bleeding during the second or third trimester include:

  1. Incompetent cervix (a premature opening of the cervix, which can lead to preterm birth)
  2. Miscarriage (before the 20th week) or intrauterine fetal death
  3. Placental abruption (when the placenta — which supplies nutrients and oxygen to the baby — separates from the wall of the uterus)
  4. Placenta previa (when the placenta covers the cervix, resulting in severe bleeding during pregnancy)
  5. Preterm labor (which might result in light bleeding — especially when accompanied by contractions, dull backache or pelvic pressure)
  6. Problems with the cervix, such as a cervical infection, inflamed cervix or growths on the cervix
  7. 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

Light bleeding, often mixed with mucus, near the end of pregnancy could be a sign that labor is starting. This vaginal discharge is pink or bloody and is known as bloody show.

Causes shown here are commonly associated with this symptom. Work with your doctor or other health care professional for an accurate diagnosis.

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Jan. 20, 2022