Utility of Follow-Up Standard Sonography for Fetal Anomaly Detection: Follow-Up Sonography for Fetal Anomaly Detection

Abstract Background In 2014, the National Institute of Child Health and Human Development Fetal Imaging Workshop consensus recommended that sonograms be offered routinely to all pregnant women. In the absence of another indication, this examination is recommended at 18 to 22 weeks of gestation. Studies of anomaly detection often focus on pregnancies at risk for anomalies and on the yield of detailed sonography – topics less applicable to counseling low-risk pregnancies about the benefits and limitations of standard sonography. The clinical utility of follow-up sonogram in low-risk pregnancies for the purpose of fetal anomaly detection has not been established. Objective To evaluate the utility of follow-up standard sonography for anomaly detection among low-risk pregnancies in a non-referred population. Study Design We performed a retrospective cohort study of singleton pregnancies that underwent standard sonography at 18-21 6/7 weeks of gestation from October 2011-March 2018 with subsequent delivery of a live-born infant at our hospital. Pregnancies with indications for detailed sonography in our system were excluded, so as to evaluate fetal anomalies first identified with standard sonography. Anomalies were categorized according to the European Registration of Congenital Anomalies and Twins (EUROCAT) system, with confirmation based on neonatal evaluation. Among those with no anomaly detected initially, we evaluated the rate of subsequent detection according to number of follow-up sonograms, gestational age at sonography, organ system(s) affected, and anomaly severity. Statistical analyses were performed using χ2 and Mantel-Haenszel test. Results Standard sonography was performed in 40,335 pregnancies at 18-21 6/7 weeks, and 11,770 (29%) had at least 1 follow-up sonogram, with a second follow-up sonogram in 3520 (9%). Major abnormalities were confirmed in 387 infants (1%), with 248 (64%) detected initially and 28 (7%) and 5 (1%) detected on the first and second follow-up sonograms. Detection of residual anomalies on follow-up sonograms was significantly lower than detection on the initial standard exam: 64% on initial exam, 45% for first follow-up, and 45% for second follow-up, P Conclusions In a low-risk, non-referred cohort with fetal anomaly prevalence of 1%, follow-up sonography resulted in detection of 45% of fetal anomalies that had not been identified during the initial standard sonogram. Significantly more follow-up sonograms were required to detect each additional anomalous fetus.