When Can Ultrasound Results Mean a Miscarriage?

How Doctors Use This Tool to Distinguish a Miscarriage From an Early Pregnancy

Transvaginal Ultrasound
Transvaginal ultrasound is generally more sensitive than abdominal ultrasound for diagnosing an early miscarriage.. Image © A.D.A.M.

When administering an early ultrasound exam, such as during the first trimester of a woman's pregnancy, it can be hard for medical professionals to distinguish an early pregnancy from a missed miscarriage. A missed miscarriage is a pregnancy loss in which the embryo has either stopped developing or was never formed, but the mother is not yet having clear miscarriage symptoms such as vaginal bleeding or spotting, the passing of tissue through the vagina, and/or pain or cramping in the abdomen, lower back, or pelvic area.

Guidelines for Diagnosing Miscarriage Through Ultrasound

To avoid a misdiagnosis, doctors use specific guidelines to determine when ultrasound results may signal a miscarriage. For example, in a report by the Society for Obstetrics and Gynecology of Canada, researchers recommended that miscarriage be diagnosed if a transvaginal ultrasound reveals the following:

  • No heartbeat in an embryo larger than 5 mm
  • Gestational sac is larger than 8mm and has no yolk sac
  • Gestational sac is larger than 16mm and has no embryo

In addition, if an earlier ultrasound revealed a fetal heartbeat and a subsequent ultrasound finds no heartbeat, this also indicates a miscarriage. Falling levels of hCG (human chorionic gonadotropin, a hormone that's made during pregnancy) alongside an ultrasound that shows an empty gestational sac or no fetal heartbeat may also lead to a miscarriage diagnosis.

How These Guidelines Vary

It's critical to note that different countries and different medical associations may vary in their exact approaches to this issue.

And, of course, as scientific research on the topic evolves, guidelines may change.

The reason that guidelines such as these are important is because most pregnancy losses occur in the first trimester.

Calculating Miscarriage Risk

Calculating a mother's risk of pregnancy loss depends largely on her age.

According to the American Congress of Obstetricians and Gynecologists, the risk of miscarriage for women changes significantly with age:

The Woman's AgeAverage Risk of Miscarriage
20-30 years old9-percent to 17-percent
35 years old20-percent
40 years old40-percent
45 years old80-percent

If You Experience a Miscarriage

If you do experience a missed miscarriage, which can be extremely traumatic (both physically and emotionally), there are resources available that can help you and your partner get through the difficult period. Ask your doctor if there are any in-person support groups in your area, and/or seek out anonymous online support. You can also check out online resources like Miscarriage Matters, a site run by a charitable organization that offers online live chats. 

More Miscarriage Resources

Understanding Types of Pregnancy Loss

What Does an Early Miscarriage Look Like?

Understanding Pregnancy Ultrasound Results

The Accuracy of Ultrasound Results

8 Common Miscarriage Misconceptions

Sources:

Morin, Lucie and Michiel C. Van den Hof, "Ultrasound Evaluation of First Trimester Pregnancy Complications." SOGC Clinical Practice June 2005. Accessed 1 June 2008.

http://www.mayoclinic.org/diseases-conditions/pregnancy-loss-miscarriage/basics/symptoms/con-20033827

http://www.mayoclinic.org/diseases-conditions/pregnancy-loss-miscarriage/basics/tests-diagnosis/con-20033827

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