[Prediction of birth weight by three-dimensional ultrasonography using fetal upper arm volume: preliminary results].
OBJECTIVE
to evaluate the accuracy of fetal upper arm volume, using three-dimensional ultrasound (3DUS), in the prediction of birth weight.


METHODS
this prospective cross-sectional study involved 25 pregnancies without structural or chromosomal anomalies. Bidimensional parameters (biparietal diameter, abdominal circumference and femur length) and the 3DUS fetal upper arm volume were obtained in the last 48 hours before delivery. The multiplanar method, using multiple sequential planes with 5.0-mm intervals, was used to calculate fetal upper arm volume. Polynomial regressions were used to determine the best equation in the prediction of fetal weight. The accuracy of this new formula was compared with Shepard's and Hadlock's formulas.


RESULTS
fetal upper arm volume was strongly correlated to birth weight (r=0.83; p<0.005). Linear regression was the best equation [birth weight=681.59 + 43.23 x fetal upper arm volume]. The fetal upper arm volume mean error (0 g), mean absolute error (196.6 g) and mean percent absolute error (6.5%) were lower than using Shepard's formula; however, the difference did not reach significance (p>0.05). Birth weight predicted by fetal upper arm volume had a mean error lower than Hadlock's formula, but this difference was not statistically significant (p>0.05).


CONCLUSIONS
the accuracy of fetal upper arm volume obtained through 3DUS is similar to the accuracy of bidimensional ultrasound in the prediction of birth weight. These findings need to be confirmed by larger studies.
Vieira
Márcio Fragoso
MF
Departamento de Obstetrícia, Universidade Federal de São Paulo, São Paulo, SP, Brasil.
Nardozza
Luciano Marcondes Machado
LM
Araujo Júnior
Edward
E
Guimarães Filho
Hélio Antonio
HA
Moron
Antonio Fernandes
AF
D000293:Adolescent; D000328:Adult; D001132:Arm / Q000000981:diagnostic imaging* / Q000196:embryology*; D001724:Birth Weight; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D011237:Predictive Value of Tests; D011247:Pregnancy; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal / Q000379:methods*; D055815:Young Adult