Study: Prenatal ultrasound screening increased substantially in past decade

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Prenatal ultrasonography has seen a substantial increase in usage rates of approximately 55 percent over the past decade, but the number does not reflect an increase in high-risk pregnancies, said a study published this week in the Canadian Medical Association Journal.

In the population-based study, John You, PhD, of McMaster University in Ontario, Canada, and colleagues wrote: “[E]fforts to promote more appropriate use of prenatal ultrasonography for singleton pregnancies appear warranted.”

Current guidelines recommend two ultrasounds throughout the course of an uncomplicated pregnancy, with one in the first trimester and one in the second to screen for fetal and genetic anomalies. However, the authors noted that close to one in five women, including those considered low-risk for birth complications, undergo four or more ultrasounds during the second and third trimester of pregnancy.

Moreover, the study found that the increase in the use of multiple ultrasound scans per pregnancy has been more pronounced in low-risk than high-risk pregnancies in their Ontario-based patient-population used in the research.

"Our findings are consistent with a growing body of evidence suggesting that some health interventions most beneficial to high-risk individuals are frequently directed at apparently low-risk populations," said the authors.

The study examined the changes in ultrasonography usage rates from 1996-2006. Including both low-risk and high-risk pregnancies (defined by the presence of a maternal co-morbidity, need for genetics counseling or a prior complicated pregnancy), the authors investigated approximately 1.4 million singleton pregnancies.

Considerations for each pregnancy studied included the recent introduction of first trimester nuchal translucency scanning, as well as demographic features including maternal age, income and rural residence. 

The researchers noted an overall increase in ultrasonography examination rates of 2,055 per 1,000 pregnancies in 1996 to 3,264 per 1,000 in 2006, with an increase noted in both low-risk and high-risk patient populations.

Ultrasound rates of at least four in the second or third trimesters were shown to have increased from 6.4 percent in 1996 to 18.7 percent in 2006, with a majority of the increase shown to be among the low-risk population, wrote the authors.

"While the benefits of prenatal ultrasound in high-risk pregnancies may be more clear, the value of repeat ultrasounds in low-risk patients is not," said You. “Since the detection of minor benign findings is increasingly more common with technological advances such as pregnancy ultrasound, they can cause anxiety and lead to invasive procedures such as amniocentesis. Increasing screening in low-risk women may also be contributing to increasing healthcare costs.”

While the authors concluded that the reasoning behind the increase in the use of prenatal ultrasonography is unknown, they surmised that obstetricians may feel the need to reassure patients with a safe and relatively cost-effective ultrasound test in order to avoid any potential legal risk.

Despite the theory however, You and colleagues stated that current practices must be reviewed and a balance between frequency and medical need should be initiated.