Are more ultrasounds better in complicated pregnancy?

Ultrasounds are among the most common tests a woman will have during any pregnancy. We use them to accurately determine the due date for a pregnancy, screen for Down syndrome, and look for the presence of fetal conditions. Ultrasounds are used even more commonly during the third trimester of a pregnancy in which the mom-to-be has a condition such as diabetes, high blood pressure, or others that can affect fetal growth and the amount of amniotic fluid around the baby.

Because of concerns about fetal growth (too big or too small) and amniotic fluid (too much or too little), we check on these patients’ babies more frequently via ultrasound leading up to birth than we would for a woman with a typical pregnancy. The goal of these increased ultrasounds traditionally has been to detect problems sooner and protect a larger number of moms and babies. 

Ultrasound in general is a highlight of pregnancy for many women, and we’ve covered the topic from many angles in this blog, including:

• 4 things to consider before inviting guests to a baby’s ultrasound
• A head-to-toe tour of your baby’s ultrasound
  
• Challenges faced with prenatal ultrasound
• Why to avoid ‘keepsake’ 3-D and 4-D ultrasounds

However, one big question remains: Do more frequent ultrasounds really help detect problems related to growth or fluid abnormalities sooner in complicated pregnancies?

As with many tests related to pregnancy, there is some disparity among medical centers about how often a woman should have ultrasounds, especially late in her pregnancy. During the third trimester, some offices perform ultrasounds every two weeks, while others (like ours) perform one every three to four weeks. To be clear, we are talking about ultrasounds that evaluate fetal growth and amniotic fluid volumes, not ultrasounds that look at fetal activities such as movement and breathing. 

Finding the answer

In spring 2018, researchers sought to answer the question as to whether more frequent ultrasounds lead to better detection of abnormalities of growth and amniotic fluid and thereby help protect a larger number of women with complex pregnancies and their babies.

Researchers in the Timing of Serial Ultrasound In At Risk Pregnancies: A Randomized Controlled Trial (SUN Trial) conducted a randomized controlled study in which they enrolled approximately 200 women with conditions that can affect a baby’s growth or the amount of amniotic fluid around it. The women were randomly divided into two groups: one received ultrasounds four weeks while the other received them twice as often (every two weeks). The study then evaluated the differences in frequency of problems that were discovered, such as abnormal growth, low fluid levels, or other complications that might prompt early delivery.

The result was a little surprising. In the end, researchers concluded that more frequent ultrasounds did not identify problems more frequently during the third trimester of complex pregnancies.

What this means for patients

Many women think of ultrasounds as fun opportunities to actually see their babies, which can be an emotional experience during pregnancy. But it’s important to understand that ultrasounds are medical exams, and we sometimes find questionable results that prompt more tests or interventions, such as hospitalization or sometimes induction of labor. Adding unnecessary tests can lead to more stress and a larger bill for patients, both of which we want to avoid.

Additionally, it already can be time-consuming and challenging for patients with complicated pregnancies to get to every prenatal appointment. If we can reduce appointments that aren’t vital, we can save patients’ time and open availability for women who really need to see a doctor.

Ultimately, doctors should base the number of ultrasounds a woman needs on her unique condition and the health of her developing baby. If any patient is concerned that she’s not getting enough ultrasounds, or perhaps that she’s having too many, we encourage her to talk to her doctor about the frequency. Every woman is her own best advocate, and healthy communication is key during any pregnancy.

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