Causes of Vaginal Bleeding During First Trimester of Pregnancy

Any vaginal bleeding during the first trimester (first 12 weeks) of pregnancy can be an indication of a serious problem such as a miscarriage or ectopic pregnancy and needs immediate medical attention. After proper evaluation, the treatment and management of the vaginal bleeding will be guided by the cause of bleeding.

Bleeding during the first trimester can vary from a dot or pinhead sized spot of blood to bleeding equivalent to a light or even heavy period. Any sign of blood from the vagina during pregnancy should be taken seriously. If there are other signs and symptoms like severe abdominal pain, fever or dizziness, immediate medical attention should be sought.

Bleeding First Trimester Causes

While spontaneous abortion or miscarriage (which includes threatened, incomplete, inevitable, complete, septic or missed) is the most common cause of vaginal bleeding in the first trimester of pregnancy, a ruptured ectopic pregnancy is the most dangerous one. There are other less serious causes which will not pose any threat to the pregnancy, however, this should be assessed by a medical professional.

  • Implantation bleeding
    • Implantation of the fertilized ovum into the uterine wall may cause a small amount of bleeding.
    • This may occur around the time of the expected period.
    • It is considered normal and does not require any treatment.
  • Threatened abortion
    • In this instance, the fetus may be under threat and a healthy pregnancy may not be possible.
    • This could be due to improper implantation of the placenta, may be associated with the use of drugs and alcohol, trauma and other underlying diseases.
    • Although the vaginal bleeding may end in a miscarriage, there is a chance of averting the danger so that pregnancy may continue to full term.
  • Incomplete abortion
    • Some of the products of conception (the fetus, placenta and membranes) have already been expelled from the uterus.
    • Pregnancy cannot continue in this case.
  • Complete abortion
    • All the products of conception have been expelled by the uterus.
  • Inevitable abortion
    • The signs and symptoms indicate that it will not be possible to save the pregnancy.
  • Missed abortion
    • In some cases, although the fetus is dead, the products of conception are still retained within the placenta.
  • Infected (septic) abortion
    • There is infection of the uterus and products of conception after abortion.
  • Ectopic pregnancy
    • The fertilized ovum is implanted in some other site (usually the fallopian tube) instead of the uterus.
    • Can pose a risk to the health of the mother.
  • Molar pregnancy
    • Instead of a fetus, a grape-like cluster of abnormal tissues grow in the uterus.
  • Post-coital bleeding
    • Bleeding after intercourse may be normal during pregnancy.
  • Trauma or injury to vaginal wall
    • May follow domestic violence or an amniocentesis or chorionic villus sampling procedure.
  • Ruptured corpus luteum cyst
  • Vaginal or cervical infection
  • Cervical cancer
  • Cervical polyps

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