Routine prenatal ultrasound screening - Tips from Other Journals

Date: Feb 1, 1994

Today many clinicians perform ultrasound screening of the fetus as part of routine prenatal care. While previous studies have found that ultrasonography improves detection of congenital anomalies, multiple gestations, placental abnormalities and errors in the assessment of gestational age, no decrease in perinatal morbidity or mortality has been demonstrated. Ewigman and colleagues performed a large, randomized study to determine whether screening ultrasonography improves perinatal outcome.

A total of 15,151 pregnant women at low risk of perinatal problems were studied. The women were randomly assigned to a control group or an intervention group that would undergo ultrasound screening at 15 to 22 weeks of gestation and again at 31 to 35 weeks of gestation. The women in the control group underwent screening with ultrasonography only for medical indications, as identified by their physicians. The definition of adverse perinatal outcome included fetal or neonatal death, as well as neonatal morbidity such as intraventricular hemorrhage.

The rate of adverse perinatal outcome among the infants of women who were randomized to receive routine ultrasound screening at both 15 to 22 weeks and 31 to 35 weeks of gestation was 5.0 percent, compared with 4.9 percent among the infants of women who underwent ultrasound screening only for medical indications. No differences were apparent between the two groups in rate of preterm delivery and distribution of birth weight. In addition, among women with postdate pregnancies, multiple-gestation pregnancies or infants who were small for gestational age, no significant differences were found in outcome.

Based on these results and the high costs associated with ultrasound screening, the authors do not recommend routine ultrasonography for pregnant women who are at low risk for perinatal morbidity or mortality.

In a related editorial, Berkowitz notes that the principal benefit of routine second-trimester ultrasonography--the detection of unsuspected fetal anomalies--must be weighed against the possibility of false-positive and false-negative results, concern about currently undocumented bioeffects of in utero exposure, and substantial costs of such screening. The author believes that in place of routine screening, physicians must be vigilant in searching for the problems or conditions that are indications for obtaining ultrasonography. (New England Journal of Medicine, September 16, 1993, vol. 329, pp. 821, 874.)

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