Accuracy of portable ultrasound for obstetric biometry

We assessed the accuracy of two portable ultrasound machines (PUM) in obtaining fetal biometry and estimating gestational age. We analyzed data from the Fetal Age Machine Learning Initiative, an observational study of pregnant women in the United States and Zambia. Each participant underwent assessment by an experienced sonographer using both a high-specification ultrasound machine (HSUM) and a PUM (either Butterfly iQ or Clarius C3) to measure fetal biometry and calculate estimated gestational age (EGA) at each visit. Through comparison of paired PUM-HSUM scans, we estimated agreement between individual biometry measurements and aggregate gestational age estimates by reporting mean difference, along with intraclass correlation coefficient (ICC) and Bland-Altman plots, adjusting for trend. 881 participants contributed 1386 paired PUM-HSUM ultrasound studies between April and December 2021. PUM studies included 991 Butterfly and 395 Clarius. Gestational age at scan ranged from 7 to 38 weeks. Compared to HSUM, the Butterfly PUM had a mean difference of -0.20 days (95%CI±0.40) in the 1st trimester and -0.68 days (95%CI±0.68) in the 2nd/3rd trimesters. Also compared to HSUM, the Clarius PUM had a mean difference of 0.47 days (95%CI±0.64) in the 1st trimester and -1.67 days (95%CI±0.43) in the 2nd/3rd trimesters. ICCs were 0.989 or greater throughout. Increasing gestational age was associated with increasing error and absolute error. Both PUM devices demonstrated a modest trend toward underestimation of EGA at advancing gestational ages in 2nd/3rd trimester scans, compared to HSUM. Both the Butterfly iQ and Clarius C3 PUM devices were highly accurate in performing fetal biometry in a diverse population from the US and Zambia. This article is protected by copyright. All rights reserved.