Universal vs selective ultrasonography to screen for large-for-gestational-age infants and associated morbidity.

OBJECTIVES: To compare the diagnostic effectiveness of selective vs universal ultrasonography as a screening test for large-for-gestational-age (LGA) infants, and to determine whether previously described ultrasound markers of excessive fetal growth could identify suspected LGA fetuses that are at increased risk of adverse neonatal outcome.

METHODS: Data from the Pregnancy Outcome Prediction study, a prospective cohort study of nulliparous women with a viable singleton pregnancy at the time of the dating ultrasound scan, were analyzed. Women were selected for clinically indicated ultrasound assessment in the third trimester as per routine clinical care, and the results of these scans were reported ('selective ultrasonography'). In addition, all participants underwent research ultrasound scans, including estimated fetal weight (EFW) assessment, at around 36 weeks' gestation, in which both the women and their clinicians were blinded to the results ('universal ultrasonography'). Participants who attended the 36-week research scan and had a live birth at the Rosie Hospital were included in the study. Screen positive for LGA was defined as EFW > 90th percentile at ≥ 34 weeks.

RESULTS: The current analysis included 3866 eligible women, of whom 1354 (35%) had a clinically indicated ultrasound scan at or after 34 weeks' gestation. A total of 177 (4.6%) infants had a birth weight > 90th percentile. The sensitivity for detection of LGA infants was 27% for selective ultrasonography and 38% for universal ultrasonography. The specificity of both approaches was high (99% and 97%, respectively). Using universal ultrasonography, neonatal outcome differed (P for interaction) by abdominal circumference growth velocity (ACGV) for both any neonatal morbidity (P = 0.08) and severe adverse neonatal outcome (P = 0.03). LGA fetuses with increased ACGV had a relative risk of any neonatal morbidity of 2.0 (95% CI, 1.1-3.6; P = 0.04) and of severe adverse neonatal outcome of 6.5 (95% CI, 2.0-21.1; P = 0.01), whereas LGA fetuses with normal ACGV were not at increased risk.

CONCLUSIONS: Third-trimester screening of nulliparous women by universal ultrasound fetal biometry increases the detection rate of LGA infants and, combined with ACGV, identifies those at increased risk of adverse neonatal outcome. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.