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Updated: May 7, 2026
High Frequency Ultrasound for the Analysis of Fetal and Placental Development In Vivo
Published on: November 8, 2018
A randomized controlled trial of third-trimester routine ultrasound in a non-selected population
Ragnhild B Skråstad1, Sturla H Eik-Nes, Oddvar Sviggum
1Faculty of Medicine, Department of Laboratory Medicine Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway; Department of Obstetrics and Gynecology, National Center for Fetal Medicine, St Olav's Hospital, Trondheim University Hospital, Trondheim, Norway.
Objective:
To compare detection rates of small-for-gestational-age fetuses, large-for-gestational-age fetuses, congenital anomalies and adverse perinatal outcomes in pregnancies randomized to third-trimester routine ultrasound or ultrasound on clinical indication.
Design:
Randomized controlled trial.
Setting:
National Center for Fetal Medicine in Norway between 1989 and 1992.
Population:
A total of 6780 pregnancies from a non-selected population.
Methods:
Two routine ultrasound examinations at 18 and 33 weeks were compared with routine ultrasound at 18 weeks and ultrasound on clinical indication. Suspected small-for-gestational-age fetuses were followed with serial scans and cardiotocography. Doppler ultrasound was not used.
Main Outcome Measures:
Detection rates of small-for-gestational-age and large-for-gestational-age fetuses, congenital anomalies and adverse perinatal outcomes.
Results:
Third trimester routine ultrasound improved detection rates of small-for-gestational-age fetuses from 46 to 80%, but overall perinatal morbidity and mortality remained unchanged. Detection of large-for-gestational-age fetuses increased from 36 to 91%. There was a significant increase of induction of labor and elective cesarean sections due to suspected small-for-gestational-age and a significant decrease of induction of labor and elective cesarean sections due to suspected large-for-gestational-age in the study group; there were no other differences regarding intervention. The detection rate of congenital anomalies was 56%, with no significant difference between the groups.
Conclusions:
Routine use of third-trimester routine ultrasound increased detection rates of small-for-gestational-age and large-for-gestational-age fetuses. This did not alter perinatal outcomes. Third-trimester ultrasound screening should not be rejected before a policy of adding Doppler surveillance to the high-risk group identified has been investigated further.
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