In a decade the use of prenatal ultrasounds in pregnant women increased by 55 per cent, suggesting a need to review current practices, says a McMaster University researcher.
In a study published in the Canadian Medical Association Journal (CMAJ), John You, an assistant professor of medicine and clinical epidemiology and biostatistics, along with researchers from McMaster and the Institute for Clinical Evaluative Sciences, found that more than one-third (37 per cent) of pregnant women now receive three or more ultrasound tests in the second and third trimesters.
The increase in the use of multiple ultrasound scans per pregnancy has been more pronounced in low-risk than high-risk pregnancies.
"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," You and his co-authors wrote.
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 study examined almost 1.4 million single-baby pregnancies between 1996 and 2006 in Ontario. It included both low-risk and high-risk pregnancies, the latter defined by the presence of a maternal co-morbidity, need for genetics counselling or a prior complicated pregnancy. The study accounted for the recent introduction of first trimester nuchal translucency scanning.
The authors found that almost one in five pregnant women — including those at low-risk of complications — now receive four or more ultrasounds in the second and third trimesters.
"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," the authors wrote.
The researchers concluded that more judicious 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.