Sixty-seven consecutive patients who delivered a newborn weighing over 3,500 g after 37 weeks of gestation
were recruited between October 1990 and January 1995. All of these infants were delivered at the same facility within one week of an ultrasound examination. Breech fetuses and twins were excluded from the study.
Estimated fetal weight (EFW) was calculated from ultrasonic measurements of biparietal diameter, anteroposterior trunk diameter, transverse trunk diameter, and femur length. Difference (EFW-birth weight
(BW)) was -196.4±326.1 g; range, -868 to 687 g. Percent difference ((EFW-BW)/BW•100) was-5.1±8.7%;
range -22.7 to 19.5%. BW correlated negatively with difference and percent difference (P2,. 171
and. 135, respectively). Thirty-five of the 67 fetuses were scanned by fellows (F) and 32 by general obstericians (GO). The difference (-117.7±291.2 g; range, -726 to 473 g) and percent difference (-3.1±7.8%;
range, -19.8% to 12.9%) in the F group were significantly smaller than those (difference (-282.4±344.7 g;
range, -868 to 687 g) and percent difference (-7.3%±9.2%; range, -22.7% to 19.5%) in the GO group,
respectively (P2,.176 and. 138, respectively). BW did not correlate with difference or percent difference in F group.
EFW tended to be underestimated in fetuses weighing over 3,500 g, especially in the GO group. There is thus
need to impreve the skill of general obstericians in establishing accurate sections for measurement and at
measuring each parameter.