Predicting birth weight by fetal upper-arm volume with use of three-dimensional ultrasonography.

ABSTRACT

PIP: The capability of fetal upper-arm volume assessed by 3-dimensional ultrasonography to predict birth weight was investigated in a prospective study involving 105 women who delivered live infants at National Cheng Kung University Hospital (Tainan, Taiwan) in 1996. Mean birth weight was 3312 grams (range, 1194-4425 g). Upper-arm volume was measured within 48 hours of delivery by both traditional 2-dimensional ultrasonography and the 3-dimensional technique. 3-dimensional ultrasonography has the advantage of being independent of fetal position and is not influenced by arm shape. Upper-arm volume was highly correlated with birth weight (p 0.0001). Through use of linear and polynomial regression, a best-fit new formula for predicting birth weight was derived: 1088.60 + 36.024 x upper-arm volume. Compared with 4 pre-existing formulas, the new formula (with upper-arm volume measured by 3-dimensional ultrasonography) had the lowest values in terms of error (0.0 g), absolute error (153.7 g), and percentage error (0.53%) in predicting birth weight. A large-scale prospective study is underway at this hospital to further validate the new formula.