News

Pregnant women having more ultrasounds despite low-risk pregnancies, study finds

January 07, 2010

By Patricia Nicholson

Pregnant women in Ontario may be having more prenatal ultrasounds than recommended, even in low-risk pregnancies. A new study found a 55 per cent jump in the number of prenatal ultrasounds performed in 2006, compared to 1996.

The study, led by researchers at McMaster University in Hamilton, Ont., included almost 1.4 million deliveries of single births from 1996 to 2006. The researchers found a steady increase in ultrasound examinations over the course of the study period, even after accounting for the recent introduction of nuchal translucency scanning to screen for Down syndrome in the first trimester.

During the study period, the ultrasound rate increased from 2,055 examinations for every 1,000 births in 1996, to 3,264 per 1,000 births in 2006.

Guidelines for uncomplicated pregnancies recommend one prenatal ultrasound during the first trimester and one in the second trimester. However, the study found that more than one-third of women (37 per cent) had three or more ultrasounds during the second and third trimesters, and almost 19 per cent of women had four or more ultrasounds in the second and third trimesters.

Those increases do not correspond with an increase in high-risk pregnancies. In fact, the increases appeared to be even more apparent in low-risk pregnancies than high-risk pregnancies. This indicates that the increase may be due to non-medical reasons, such as patient reassurance, patient demand and the cautious approach some doctors have adopted to protect themselves against lawsuits.

The study authors noted that although the benefits of repeat ultrasounds in high-risk pregnancies are clear, there is no evidence that repeat ultrasounds benefit women with low-risk pregnancies.

The study was published in the Jan. 4, 2010 issue of CMAJ.

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