Some pregnant women have some vaginal bleeding during the first 3 months of pregnancy. Bleeding may occur with or without abdominal cramps. When the symptoms indicate a miscarriage is possible, the condition is called a "threatened abortion." (This refers to a natural event that is not due to a medical or surgical abortion.)

Miscarriage is common. Small falls, injuries or stress during the first trimester of pregnancy can cause threatened miscarriage. It occurs in almost one half of all pregnancies. The chance of miscarriage is higher in older women. About one half of women who have bleeding in the first trimester will have a miscarriage.

Symptoms of a threatened miscarriage include:

• Vaginal bleeding during the first 20 weeks of pregnancy (last menstrual period was less than 20 weeks ago). Vaginal bleeding occurs in almost all threatened miscarriages.
• Abdominal cramps may also occur. If abdominal cramps occur in the absence of significant bleeding, consult your health care provider to check for other problems besides threatened miscarriage.

Note: During a miscarriage, low back pain or abdominal pain (dull to sharp, constant to intermittent) can occur. Tissue or clot-like material may pass from the vagina.

Your provider may perform an abdominal or vaginal ultrasound to check the baby's development and heartbeat, and the amount of bleeding. A pelvic exam may also be done to check your cervix.

Blood tests done may include:

• Beta HCG (quantitative) test (pregnancy test) over a period of days or weeks to confirm whether the pregnancy is continuing
• Complete blood count (CBC) to determine the presence of anemia
• Progesterone level
• White blood count (WBC) with differential to check for infection

Apart from controlling the blood loss, you may not need any particular treatment. If you are Rh Negative, then you may be given immune globulin. You may be told to avoid or restrict some activities. Not having sexual intercourse is often recommended until the warning signs have disappeared. 

Most women with a threatened miscarriage go on to have a normal pregnancy.

Women who have had two or more miscarriages in a row may be more likely than other women to miscarry again.

Complications may include:

• Anemia from moderate to heavy blood loss, which may require a blood transfusion.
• Infection.
• Miscarriage.
• The provider will want to ensure that the symptoms are not due to an ectopic pregnancy. This is a potentially life-threatening complication.

If you know you are (or are likely to be) pregnant and you have any symptoms of threatened miscarriage, contact your prenatal provider right away.

Most miscarriages cannot be prevented. The most common cause of a miscarriage is a random genetic abnormality in the developing pregnancy. If you have two or more repeated miscarriages, you should consult a specialist to look for an underlying condition that is causing the problem. Women who get prenatal care have better pregnancy outcomes for themselves and their babies. 

A healthy pregnancy is more likely when you avoid things that are harmful to your pregnancy, such as:

• Alcohol
• Infectious diseases
• High caffeine intake
• Recreational drugs
• X-rays

Taking a prenatal vitamin or folic acid supplement before becoming pregnant and throughout your pregnancy can lower your chance of miscarriage and improve the chance of delivering a healthy baby.

It is better to treat health problems before you get pregnant than to wait until you are already pregnant. Miscarriages caused by diseases that affect your whole body, such as high blood pressure, are rare. But you can prevent these miscarriages by detecting and treating the disease before becoming pregnant.

Other factors that can increase your risk for miscarriage include:

• Obesity
• Thyroid problems
• Uncontrolled diabetes

Threatened miscarriage; Threatened spontaneous abortion; Abortion - threatened; Threatened abortion; Early pregnancy loss; Spontaneous abortion 

Henn MC, Lall MD. Complications of pregnancy. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 173.

Richards DS. Obstetric ultrasound: imaging, dating, growth, and anomaly. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 9.

Turocy J, Williams Z. Early and recurrent pregnancy loss: etiology, diagnosis, treatment. In: Gershenson DM, Lentz GM, Valea FA, Lobo RA, eds. Comprehensive Gynecology. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 16.

Updated by: John D. Jacobson, MD, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.