Journal of Ultrasound in Medicine, Vol 1, Issue 3 97-104, Copyright © 1982 by American Institute of Ultrasound in Medicine
Fetal biparietal diameter: a critical re-evaluation of the relation to menstrual age by means of real-time ultrasound
F. P. Hadlock, R. L. Deter, R. B. Harrist and S. K. Park
Department of Radiology, Jefferson Davis Hospital, Houston, TX 77019.
The relationship between fetal biparietal diameter (BPD) and menstrual age
was determined by cross-sectional analysis of 533 fetuses (12 to 40 weeks)
examined with a linear array real-time (dynamic image) scanner using
specifically defined methodology. Mathematical modeling of the data
demonstrated that the optimal fit was the linear cubic function (r2 = 99
per cent); predicted BPD values calculated from the function were most
comparable with composite data from cross-sectional studies performed with
static scanners after 1974 (average difference, 0.22 mm) and least
comparable with composite data from cross-sectional studies performed with
static scanners before 1974 (average difference, 2.0 mm). The variability
associated with predicting menstrual age from the BPD increased
progressively throughout gestation; the maximal variability was noted
between 36 and 42 weeks (+/- 3.6 weeks). Comparison with our longitudinal
study of BPD growth indicates that the cross-sectional data represent a
valid estimate of the true longitudinal BPD growth curve of the population.
