Journal of Ultrasound in Medicine, Vol 14, Issue 11 829-836, Copyright © 1995 by American Institute of Ultrasound in Medicine
Normal interval fetal growth rates based on obstetrical ultrasonographic measurements
L. N. Nazarian, E. J. Halpern, A. B. Kurtz, W. W. Hauck and L. Needleman
Department of Radiology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
Analyzing fetal interval growth may improve detection of growth
abnormalities. This study establishes normal limits for growth rates of
fetal biparietal diameter, abdominal diameter, abdominal circumference, and
femur length. Fetal measurements were obtained during 1450 obstetrical
sonographic examinations in 510 patients with normal-weight term
deliveries. Using a random-effects model for longitudinal data, cubic
curves of size versus mean gestational age were fitted using a restricted
maximum likelihood technique. Quadratic growth rate curves were then
calculated as derivatives of the fitted curves. The growth rate equations
are as follows: Biparietal diameter growth rate = 2.59 + 0.127 (MGA) -
0.000447 (MGA)2; abdominal diameter growth rate = 3.61 + 0.0325 (MGA) -
0.0017 (MGA)2; abdominal circumference growth rate = 11.3 + 0.102 (MGA) -
0.00534 (MGA)2; and femur length growth rate = 5.49 - 0.17 (MGA) + 0.00181
(MGA)2. Rates are expressed in mm/wk and mean gestational age in wk.
Because standard deviations depend on the time interval between
examinations, separate growth rate tables are provided for intervals of 4,
6, 8, and > or = 10 weeks.
