A randomized trial of routine prenatal ultrasound

Nine hundred fifteen of 2171 pregnant patients had no indication for ultrasound at their first prenatal visit and were randomly assigned to receive either a single routine screening ultrasound or usual prenatal care. The estimated date of confinement was altered in 24.9% of routine-ultrasound patients and in 11.6% of usual-care patients through ultrasound examinations obtained for a subsequent clinical indication. Of these, 8.3% of routine-ultrasound and 5.2% of usual-care patients had gestational age errors of 2 weeks or more. There were no differences between the groups in inductions for post-dates pregnancy (7.0 versus 7.5%; P = .87), total inductions (22.6 versus 24.9%; P = .61), or adverse perinatal outcomes (6.7 versus 8.3%; P = .63). Both sets of twins were detected in the screened group. In the usual-care group, five of seven pairs of twins (71%) were diagnosed by 24 weeks' gestation. There was no benefit found from routine ultrasound as performed in this study.