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353: Sonographic predictors of fetal fat accretion

      Objective

      Data suggest that the in-utero environment affects neonatal body composition which is predictive of childhood obesity and metabolic syndrome. Percent fat at birth correlates poorly with birthweight (BW) and is more predictive than BW of offspring metabolic complications in later life. There are few data on the use of ultrasound (US) to predict neonatal adiposity yet US remains the basis for predicting abnormal growth and is necessary for any future fetal-based strategy. This study was undertaken to evaluate US measures of fetal adiposity and to correlate them with neonatal body composition.

      Study Design

      Obese and normal weight women carrying normal singleton pregnancies were prospectively enrolled at 14 weeks. Multiple US measures of fetal size and fat accretion (subcutaneous tissue area) were performed at 28 and 36 wks. These were compared with BW and with neonatal body composition as measured by dual x-ray absorptiometry (DXA).

      Results

      Among 9 women enrolled in the study, neonatal body composition ranged from 6-19% fat and correlated poorly with birth weight (R2=0.085, NS). However, body composition correlated well with mid-femur (R2=0.74, p=0.003) and mid-humerus (R2=0.59, p=0.015) cross-sectional area of subcutaneous (adipose) tissue at 36 weeks, and with femur length (R2=0.45, P = 0.047) at 28 weeks. The AC at 36 weeks was not predictive of % fat at birth (R2=0.16). Liver length at 36 weeks was most predictive of neonatal adiposity with an R2 of 0.95, p=0.008 (Figure).
      Figure thumbnail gr1
      Fetal liver length predicts neonatal % body fat

      Conclusion

      This is the first study to demonstrate that fetal liver length and subcutaneous tissue (mid-femur & mid-humerus) correlate with neonatal % body fat. As previously published, BW and neonatal body composition did not correlate. These observations hold practical implications for antenatal estimation of fetal fat accretion and may be clinically useful in the development of a fetal-based strategy directed toward the prevention of neonatal adiposity and later childhood obesity.