Journal of Ultrasound in Medicine, Vol 12, Issue 8 431-436, Copyright © 1993 by American Institute of Ultrasound in Medicine
Long-term prediction of birth weight
J. J. Santonja-Lucas, C. Armero and L. Martinez-Gonzalez
Department of Pediatrics, Obstetrics and Gynecology, University of Valencia, Facultat de Medicina i Odontologia, Spain.
On the basis of the hypothesis that undisturbed individual growth in fetal
life keeps a constant proportional difference with the standard population
50th percentile, birth weight can be predicted with a single sonographic
exploration after the 16th week of pregnancy. Data on 135 singleton
pregnancies with accurate dates and delivery at term were used. Sonography
was performed between the 17th and 36th weeks of pregnancy, in every case
at least 4 weeks before delivery. The observed measurements of BPD, FL, and
AC were used for the prediction of their values on the day of delivery,
applying the Hadlock equation for the estimation of birth weight. The mean
error of birth weight predictions was -1 +/- 11% (SD), with a correlation
coefficient between observed and predicted birth weights of 0.62 (P <
0.001). The accuracy was not influenced by the gestational age at the time
of exploration. The model underpredicts birth weight of larger fetuses
while overpredicting that of lighter ones, but a part of the error could be
explained by a change in the growth pattern after modeling. Regardless of
the classification considered (i.e., gestational age at sonography or birth
weight), over 83% of predictions had an error below 15%. The underlying
hypothesis could be useful clinically in modeling and monitoring fetal
growth, allowing application of the results of remote sonographic
explorations in clinical management. In addition, being able to project
fetal weight to the 40th week also is valuable in improving the patient's
understanding of fetal growth.
