Current guidelines recommend two ultrasounds in an uncomplicated pregnancy--one in the first trimester and one in the second to screen for fetal and genetic anomalies.
The new data, published in the January 2010 issue of the Canadian Medical Association Journal (CMAJ), included almost 1.4 million singleton pregnancies between 1996 and 2006 in Ontario, Canada's most populous province. It included both low-risk and high-risk pregnancies, the latter defined by the presence of a maternal comorbidity, need for genetics counseling, or a prior complicated pregnancy. The study accounted for the recent introduction of first trimester nuchal translucency scanning.

The investigators discovered that almost one in five of all pregnant women--including those at low-risk of complications--now receive four or more ultrasounds in the second and third trimesters. "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,” reported Dr. John You, from McMaster University (Hamilton, Ontario, Canada) and coauthors.

Obstetricians practice in the highest medical-legal risk environment and may feel the need to reassure patients with a safe and relatively cost-effective ultrasound test. "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,” wrote the authors. 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.”

The investigators concluded that more careful use of prenatal ultrasounds in low-risk women is required, but there should be careful discussion over the best approach to balance frequency and medical need.

Related Links:
McMaster University