EVALUATION OF ROUTINE ULTRASOUND IN THE PRENATAL-DIAGNOSIS OF STRUCTURAL ANOMALIES OF THE FETUS

The objective of this study was to evaluate routine obstetric ultrasou nd in detecting fetal structural anomalies and the impact of changing clinical practice on success rates, A retrospective study of routine u ltrasound in a population of 6,869 pregnancies was performed during 19 85-86 (phase 1) to establish efficacy of ultrasound in the detection o f fetal anomalies, Changes in ultrasound practice comprised timing, pe rsonnel and technique of fetal examination, After alterations in pract ice, a prospective study of 6,969 pregnancies during 1987-89 (phase 2) was performed. All abnormal fetuses (cases) were assessed in both stu dies. Random samples of normal infants (controls) were chosen from bot h populations to establish specificity, In 83 cases in phase 1,116 ano malies were diagnosed postnatally of which 11 were suspected by routin e prenatal ultrasound at < 24 weeks (sensitivity 9%, 95% C.I. 4-15), I n 72 cases in phase 2, 89 anomalies were identified postnatally of whi ch 27 were suspected by routine prenatal ultrasound at <24 weeks (sens itivity 30%, 95% C.I. 21-41), The change in sensitivity was statistica lly significant (p=0.0003). Of the 382 control infants randomly select ed in phase I, false abnormal scans were not identified (specificity 1 00%, 95% C.I. 99-100). Of the 367 control infants in phase 2, 12 false abnormal scans were identified (specificity 96.7%, 95% C.I. 95-99). T he decrease in specificity was statistically significant (p=0.0013). T he detection of urorenal and to a lesser degree central nervous system anomalies showed most improvement between the two phases, The alterat ions to routine ultrasound practice in timing, personnel and technique have significantly improved the detection of all fetal structural ano malies but at the cost of a small but significant loss of specificity.