The Fetal Arm: Individualized Growth Assessment in Normal Pregnancies

• Published in: Journal of ultrasound in medicine 2005-06, Vol.24 (6), p.817-828
• Main Authors: Lee, Wesley, Deter, Russell L, McNie, Beverley, Goncalves, Luis F, Espinoza, Jimmy, Chaiworapongsa, Tinnakorn, Balasubramaniam, Mamtha, Romero, Roberto
• Format: Article
• Language: English
• Subjects: Arm - diagnostic imaging; Arm - embryology; Female; Fetal Growth Retardation - diagnosis; Fetus - anatomy & histology; Humans; Male; Models, Theoretical; Pregnancy; Pregnancy Trimester, Third; Prospective Studies; Ultrasonography, Prenatal
• ISSN: 0278-4297; 1550-9613
• DOI: 10.7863/jum.2005.24.6.817

The goals were to introduce fractional arm volume (AVol) as a new soft tissue parameter of fetal growth assessment and to develop individualized growth standards, based on Rossavik models, for AVol, midarm circumference (ArmC), and humeral diaphysis length (HDL). A prospective longitudinal study of 22 fetuses was conducted using 2- and 3-dimensional sonography. Three new growth parameters (HDL, ArmC, and AVol) were used to establish individualized standards for arm growth with the use of Rossavik functions [P=c(t)k (+) s(t), where P is the anatomic parameter; c, k, and s are model coefficients; and t is the time variable]. Second-trimester models were specified from the linear slopes of growth curves before approximately 28.0 menstrual weeks. For a given fetus, normal third-trimester trajectories were predicted for each parameter. Observed and predicted measurements were compared by percent deviations. Rossavik functions fit all parameter trajectories extremely well (R(2)=95.7%-99.4%). By fixing coefficients k at their mean values, their respective fits did not change, and the variabilities of both coefficients c and s were reduced. Coefficient c was also significantly related to second-trimester slope, as was s to c, for all 3 parameters (R(2)=97.7%-98.7%; P