EFFECT OF AMNIOTIC-FLUID VOLUME ON ULTRASONIC FETAL WEIGHT ESTIMATION

We evaluated the relationship between the amniotic fluid index and the accuracy of fetal weight estimation using ultrasonography. Six hundre d, and sixty-four patients, between 20 and 42 weeks' gestational age, who were delivered within 1 week of a sonographic examination were stu died. Five formulas for estimating fetal weight also were studied. Sys tematic and random errors in predicting birth weight were analyzed rel ative to birth weight and amniotic fluid index. The accuracy of sonogr aphic fetal weight estimation was independent of amniotic fluid index across all gestational ages and birth weights. Each of the five formul as had similar error percentages, and no significant differences were detected. Predicted fetal weight was significantly underestimated with each of the formulas studied, a finding that was also independent of birth weight and amniotic fluid index. We conclude that ultrasonograph y can be used reliably to estimate fetal weight in patients with alter ed amniotic fluid volumes.