What to Expect From an Ultrasound for Suspected Miscarriage

An ultrasound is a diagnostic medical imaging test that uses high-frequency sound waves to form an image of something in the body. Doctors routinely use ultrasound about halfway through pregnancy to check that the baby is developing normally but may use it earlier to confirm or rule out a miscarriage.

How the Exam Is Performed

In early pregnancy, when most miscarriages occur, the ultrasound is likely to be transvaginal in order to get the best picture of the developing gestational sac and baby. In a transvaginal ultrasound, the technician or doctor will ask the woman to undress from the waist down and put on a medical gown. The technician will then insert a probe into the vagina to get an image of the uterus and fallopian tubes.

In an abdominal ultrasound, the woman will not usually need to disrobe. The technician will expose her abdomen, spread some imaging gel, and move a hand-held probe over her abdomen to get the pictures.

Exam Preparation

Transvaginal ultrasounds do not require any preparation, but for an abdominal ultrasound in early pregnancy, you may need to drink 2 to 3 glasses of water and avoid using the bathroom for about an hour before the test. Having a full bladder positions your uterus to get the best picture.

Side Effects

Most of the time, ultrasounds do not have any side effects other than possible discomfort from having a full bladder. The procedure is not painful, although a transvaginal ultrasound is more invasive and may make some women feel awkward.

Ultrasounds are generally considered safe. One study suggested that very frequent ultrasound use may cause developmental problems but other studies have found no such risks.

What Technicians Look For

For threatened or suspected miscarriages, the technician will make sure that the pregnancy is visible in the uterus (otherwise it might be an ectopic pregnancy).

The technician will usually take measurements of the sac and the developing baby for the doctor to compare with the expected measurements for the gestational age. The technician may also look for the baby's heartbeat, depending on how far along the woman is in the pregnancy.

What the Picture Looks Like

The images from an ultrasound are typically black and white and grainy in quality. Sometimes, from a patient's perspective, it can be hard to tell what it is you're seeing, but the images provide valuable information to your doctor.

How Doctors Interpret Results

Doctors frequently order ultrasounds as a part of the diagnostic workup when a woman is having miscarriage symptoms. By comparing ultrasound measurements with other diagnostic information, such as the date of the woman's last menstrual period or her hCG levels, the doctor can determine the likelihood of whether or not the pregnancy is viable.

Sometimes a doctor will order a second ultrasound after a few days or a week in order to rule out the possibility that a developing baby is small due to incorrect gestational age calculations, which might be the case in women with irregular menstrual cycles.

If an ultrasound reveals that the baby has a heartbeat, the odds of miscarriage drop drastically. If a baby's heartbeat is detected on the ultrasound, the risk of miscarriage drops to 4.5% for moms younger than 36. The risk of miscarriage after finding a heartbeat is 10% for moms 36-39 years old and 29% for women 40 or older. Women with a history of recurrent pregnancy loss have a 22% risk of miscarriage across ages.