Fetal body composition and volumes study

Abstract

Classification of abnormal fetal growth as “restriction” or “overgrowth” during an ongoing pregnancy is an important clinical challenge. Fetal soft tissue may reflect some of the earliest changes that occur in pathologic growth compared to traditional 2-dimensional (2D) estimates of fetal biometry. The Fetal 3D Study was designed to develop research and clinical applications for fetal soft tissue and organ volume assessment. Data collected in the NICHD Fetal Growth Studies included 2D fetal biometrics and 3D fetal volumes which were banked. In the Fetal 3D Study, sonographers performed longitudinal 2D and 3D measures targeting specific fetal anatomic structures. Each woman with a singleton had up to six research ultrasound scans while twins had up to seven. Of 2,802 with a singleton, 2,751 (98.2%) had 2D abdomen or 3D available and were included in the Fetal 3D Study. Of these, 2,435 (88.5%) had at least one 3D available (while 11.5% had only 2D abdomen) and 2,333 (84.8%) had at least one 3D that was measured. Out of 171 with a twin, there were 165 (96.5%) included: all had at least one 3D volume available and 152 (92.1%) had at least one 3D volume measured. Volume types with highest number of measures available were for the cerebellum, abdomen (liver and kidney) and thigh, based on protocol prioritization. After the first trimester, availability of 3D decreased with advancing gestational age (Table). For fetal organs with left and right sides (lungs, kidneys, and adrenal glands), it was more common that either side was able to be measured rather than both sides. Reliable 2D and 3D fetal biometry measurements depended on several factors including examiner training and experience, image quality, technique used to scan anatomic structures, fetal movement and position, and availability of 3D ultrasound software tools that allow rapid and reproducible measurements. Standardized procedures resulted in a large quantity of longitudinal fetal soft tissue and organ volume measurements from a diverse pregnant U.S. sample.