244: Correlation of 3D fractional limb volumes of the fetal thigh in fetal growth restriction (FGR) with normal and abnormal doppler studies

Fractional limb volume (FLV) measurements have been used to show that soft tissue measurements of the fetal thigh at 28 weeks in normal pregnancies correlate well neonatal percent body fat (JUM, 2016). With 80% of fetal fat accumulating after 28 weeks gestation, there is the possibility that assessment of fat mass could identify fetuses that are normal or pathologically small. The objective of this study was to assess the correlations between thigh volumes by FLV measurements in FGR fetuses with normal and abnormal Doppler studies. In this prospective cohort study of 49 fetuses with EFW <10th percentile for gestational age (GA), 90 ultrasound (US) exams were performed between 26-39 weeks for EFW assessment, umbilical artery (UA) PI, MCA PI and CPR measurements, and 3D volume acquisition. FGR fetuses with normal and abnormal Dopplers were grouped together. 3D FLV were done by estimating the total thigh volume (TTV) along the mid 50% of the femur using a 5-slice technique. 3D FLV technique allows for subcutaneous fat (SQ) and lean mass (LM; bone + muscle) volume assessments. Spearman’s correlation was used to assess the relationship of the different thigh volumes with EFW, abdominal circumference and Dopplers. TTV, SQ, and LM all correlate strongly with EFW and abdominal circumference (AC) at the time of measurement from 28-39 weeks GA (Table). Additionally, TTV, SQ and LM all show a significant but modest correlation with umbilical artery PI (Figure), but not with MCA PI (Table).View Large Image Figure ViewerDownload Hi-res image Download (PPT) The strong correlation between the TTV, SQ and LM with EFW and AC suggests that all these measures reflect somatic growth. The inverse correlation of the different FLV thigh measurements (as well as AC and EFW) with UA PI, but not MCA or CPR, is consistent abnormal placental vasculature and insufficiency that makes the UA PI abnormal and lead to FGR, whereas the cerebral circulation and the MCA are responding to the known effect of hypoxia and perhaps have less of an effect on somatic (TTV, SQ and LM) growth. Additional comparisons of thigh measurements of FGR fetuses with normal to those with abnormal Dopplers are needed. (Funded by The Perelman IUGR Study)