EFFECT OF PRENATAL ULTRASOUND SCREENING ON PERINATAL OUTCOME

Background. Many clinicians advocate routine ultrasound screening duri ng pregnancy to detect congenital anomalies, multiple-gestation pregna ncies, fetal growth disorders, placental abnormalities, and errors in the estimation of gestational age. However, it is not known whether th e detection of these conditions through screening leads to interventio ns that improve perinatal outcome. Methods. We conducted a randomized trial involving 15,151 pregnant women at low risk for perinatal proble ms to determine whether ultrasound screening decreased the frequency o f adverse perinatal outcomes. The women randomly assigned to the ultra sound-screening group underwent one sonographic examination at 15 to 2 2 weeks of gestation and another at 31 to 35 weeks. The women in the c ontrol group underwent ultrasonography only for medical indications, a s identified by their physicians. Adverse perinatal outcome was define d as fetal death, neonatal death, or neonatal morbidity such as intrav entricular hemorrhage. Results. The mean numbers of sonograms obtained per woman in the ultrasound-screening and control groups were 2.2 and 0.6, respectively. The rate of adverse perinatal outcome was 5.0 perc ent among the infants of the women in the ultrasound-screening group a nd 4.9 percent among the infants of the women in the control group (re lative risk, 1.0; 95 percent confidence interval, 0.9 to 1.2; P = 0.85 ). The rates of preterm delivery and the distribution of birth weights were nearly identical in the two groups. The ultrasonographic detecti on of congenital anomalies had no effect on perinatal outcome. There w ere no significant differences between the groups in perinatal outcome in the subgroups of women with post-date pregnancies, multiple-gestat ion pregnancies, or infants who were small for gestational age. Conclu sions. Screening ultrasonography did not improve perinatal outcome as compared with the selective use of ultrasonography on the basis of cli nician judgment.