Journal of Ultrasound in Medicine, Vol 10, Issue 3 149-151, Copyright © 1991 by American Institute of Ultrasound in Medicine
Amniotic fluid volume in large-for-gestational-age fetuses of nondiabetic mothers
C. B. Benson, B. F. Coughlin and P. M. Doubilet
Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115.
Large-for-gestational-age (LGA) fetuses, especially those whose birth
weight is greater than 4000 g, are at elevated risk for obstetrical
complications. Prenatal diagnosis of the condition has been limited by the
inaccuracy of fetal weight estimation and by low positive predictive values
of other sonographic parameters. We studied 412 fetuses, 35 LGA and 377
non-LGA, who were scanned within 1 week of delivery, to determine if
assessment of amniotic fluid volume can be used to improve the accuracy of
fetal weight estimation for diagnosing or excluding LGA. In our study, the
positive and negative predictive values of fetal weight estimation alone
were 47% and 95%, respectively. The distribution of amniotic fluid volumes
in LGA and non-LGA fetuses differed significantly (P less than .001).
Polyhydramnios occurred more frequently in LGA fetuses than non-LGA fetuses
(17% vs 8%) but had little effect on the positive predictive value of a
fetal weight estimate above the 90th percentile. Oligohydramnios occurred
less frequently in LGA than non-LGA fetuses (3% vs 19%) and improved the
negative predictive value of fetal weight estimation. In particular, the
combination of oligohydramnios and a fetal weight estimate below the 90th
percentile virtually excluded the possibility of LGA.
