Detection of small-for-gestational-age fetuses by ultrasound screening in a high risk population: a randomized controlled study

OBJECTIVE: To assess the value of fetal weight estimation during routine third trimester ultrasound examinations for the identification of small-for-gestational-age (SGA) fetuses, to promote active pregnancy management and so reduce perinatal morbidity.

DESIGN: A prospective controlled randomized study.

SETTING: Outpatient clinic at the Department of Obstetrics, Herlev University Hospital, Denmark.

SUBJECTS: One thousand pregnant women considered at risk were selected consecutively from April 1985 to September 1987 and randomized to either a revealed-results group or a withheld-results group.

INTERVENTION: All the women had an early ultrasound examination for estimation of gestational age. Both groups had routine ultrasound estimates of fetal weight after 28 weeks and then every third week until delivery. The results were available for clinical use only in the revealed group.

MAIN OUTCOME MEASURES: Number of interventions during pregnancy (admission to hospital, elective delivery), emergency intervention during labour, and fetal outcome.

RESULTS: Revealing the results of ultrasound estimates of fetal weight for gestational age during the third trimester resulted in statistically significantly increased diagnosis of SGA fetuses, of elective deliveries based on this diagnosis, and of healthy preterm babies admitted to the neonatal care unit, but no detectable overall improvement in weight for gestational age at birth, or in neonatal morbidity or mortality.

CONCLUSION: This method of screening improved the diagnosis of SGA fetuses, but this was not followed by improved fetal outcome.