Many pregnant women experience bleeding and spotting during the first trimester. However, not all first trimester bleeding or spotting is dangerous, but medical assessment is essential.

Doctors can diagnose first trimester bleeding with various tests. Once they determine the cause, they can discuss appropriate treatment or management.

In this article, we discuss causes, symptoms, when to see a doctor, and how doctors manage and treat first trimester bleeding.

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Not all causes of trimester bleeding are serious.

About 15–25% of pregnant women will experience bleeding in the first trimester.

Some causes of first trimester bleeding are serious, whereas others are not. Possible causes of first trimester bleeding include:

  • implantation bleeding
  • subchorionic hemorrhage
  • early pregnancy loss
  • infections and inflammation
  • ectopic pregnancy

Read on for more information about these potential causes of first trimester bleeding:

Implantation bleeding

Light bleeding may occur 1 or 2 weeks after the fertilized egg implants into the endometrial wall. This common symptom is known as implantation bleeding and is not a cause for concern.

During pregnancy, the body extends blood vessels into the uterus to support the growth of the embryo and uterine lining. The cervix may bleed more easily in the first few weeks after conception, particularly during sexual intercourse, pap smears, and pelvic exams.

Learn more about implantation bleeding here.

Subchorionic hemorrhage

A subchorionic hemorrhage is when bleeding occurs between the chorion and the uterine wall. The chorion is a membrane that surrounds the embryo that implants into the uterine wall. The chorion eventually forms the placenta.

A diagnosis of a subchorionic hemorrhage usually occurs during an ultrasound. This condition can affect even uncomplicated pregnancies.

Subchorionic hemorrhage in early pregnancy may increase the risk of preterm delivery and spontaneous abortion.

Learn more about subchorionic hemorrhage here.

Early pregnancy loss

Doctors define early pregnancy loss as a nonviable pregnancy. People may also refer to this as spontaneous abortion or miscarriage.

Learn more about pregnancy loss here.

There are several causes of early pregnancy loss. Some common causes in the first trimester include:

Ectopic pregnancy

Doctors diagnose ectopic pregnancies when they detect a fetal heartbeat outside of the uterus. This indicates that the embryo implanted in an area outside of the womb.

Since embryos cannot survive outside of the womb, ectopic pregnancies cannot reach full term.

Ectopic pregnancies can be life-threatening, and medical intervention and careful monitoring is essential.

Learn more about ectopic pregnancy here.

Gestational trophoblastic disease

Women with gestational trophoblastic disease will have masses of tissue in the uterus that are visible on ultrasound images. To prevent complications, a doctor will remove the tissue from the uterus. Surgery is the only treatment option for gestational trophoblastic disease.

In most cases, this condition will prevent a pregnancy from reaching full term.

Anembryonic pregnancy

In an anembryonic pregnancy, a gestational sac forms in the uterus without an embryo. Because of this, there is no embryo to develop into a fetus, and pregnancy loss occurs.

Incomplete abortion

When a woman an incomplete abortion occurs, some, but not all the embryonic material pass through the vagina.

Infections and other nonobstetric causes

If a doctor rules out the above causes of early pregnancy loss, they will recommend tests to rule out other conditions that may cause bleeding, including:

  • inflammation of the cervix
  • infections of the bladder or vagina
  • cancer
  • polyps
  • hemorrhoids

If a doctor diagnosis any of these conditions, they will recommend medical management to prevent pregnancy complications.

Implantation bleeding causes light bleeding or spotting without other symptoms. Sometimes pregnant women mistake implantation bleeding for their period, since it may occur around the same time a period is expected.

With early pregnancy loss, women may experience other symptoms, such as uterine cramping. Another less noticeable sign of early pregnancy loss is the disappearance of common pregnancy symptoms, such as nausea.

If an infection causes first trimester vaginal bleeding, women may experience fever, difficulty or pain during urination, and tenderness in or around the vagina, depending on the type of infection.

Women with a ruptured ectopic pregnancy require immediate medical attention. Symptoms they may experience include shoulder pain, absent bowel sounds, and a distended abdomen.

Implantation bleeding does not require treatment as it is a normal process in the first trimester and has no complications.

Most pregnancy loss occurring in the first trimester happens spontaneously and completely without intervention.

Alternatively, expectant management involves watching and waiting for the impending abortion to occur spontaneously. It can be an effective strategy except for an ectopic or a molar pregnancy.

Sometimes, doctors prescribe medication, including misoprostol (Cytotec), to help manage a pregnancy loss. These medications often replace the need for dilation and curettage, which is a procedure to remove tissue and other contents from the uterus.

Medical treatment with misoprostol can cause heavy bleeding but less pain than surgery. Surgery often causes more trauma and may lead to infection.

However, the type of treatment a woman undergoes will depend on her suitability, personal preferences, and availability of resources. A woman experiencing a pregnancy loss during the first trimester should discuss all her options with her doctor.

Pregnant women experiencing bleeding in the first trimester or at any point during the pregnancy should speak with a doctor.

A doctor will probably order blood tests and conduct vaginal examinations to determine the cause of the bleeding. Not all bleeding indicates pregnancy loss. If the doctor suspects a pregnancy complication, they will discuss the appropriate management, which may include watchful waiting, medication, or surgery.

First trimester bleeding is a common occurrence. In some situations, bleeding may indicate possible early pregnancy loss.

Doctors will first determine the cause of the bleed. Sometimes the bleeding is not dangerous, such as with implantation bleeding. Other causes of vaginal bleeding require monitoring, as with subchorionic hemorrhages.

Pregnant women who experience bleeding at any point during their pregnancy should consult a doctor so that they can identify and address the underlying cause.