Nomograms of the axial fetal cerebellar hemisphere circumference and area throughout gestation

Objective The widely applied transcerebellar diameter (TCD) obtained at axial cranial imaging, measures the distance between the lateral aspects of the cerebellum and incorporates the width of the cerebellar vermis. Our objective was to create reference ranges of axial fetal cerebellar hemisphere circumference (CHC) and area (CHA), independent of the cerebellar vermis, throughout gestation. Methods This cross-sectional study involved pregnant patients between 14 and 4.1. weeks of gestation. Inclusion criteria consisted of well-establisbed dates (confirmed by early ultrasound), non-anomalous singleton fetuses and intact amniotic membranes. Sonograpbic measurements included biparietal diameter (BPD), bead circumference (FIC), abdominal circumference (AC), femur length (FL), humerus length (HL), TCD, and estimated fetal weight (EFW). Values of axial fetal CHC and CHA were each calculated as the mean of three separate measurements. The 5(th), 50(th) and 95(th) centiles were estimated at each week of gestational age (GA) by least-squares regression for the mean and standard deviation (SD) of the CHC and CHA as functions of GA. r(2) and associated P-values for the relationships of CHC and CHA with other sonograpbic biometric measurements were calculated. Results The study included 651 consecutive patients. All attempts at obtaining axial fetal CHC and CHA were successful. Mean maternal age was 27.3 +/- 6.7 years, median gravidity was 1 (range 1-16), and median parity was 1 (range 0-6). Mean CHC (cm) throughout gestation was modeled as -2.091 + 0.2563 x GA (weeks) (SD = -0.075 + 0.0164 x GA), and mean CHA (cm(2)) was modeled as 0.245-0.0765 x GA+ 0.00506 x GA(2) (SD = 1.167 - 0.1565 x GA + 0.006785 x GA(2) - 0.00008028 x GA(3)). Fetal axial CHC and CHA correlated significantly and strongly with BPD, PHC, AC, HL, FL, TCD and EFW (all R-2 values were >= 0.95, and all P-values were < 0.001). Conclusion Nomograms of axial fetal cerebellar hemisphere circumference and area throughout gestation, independent of the cerebellar vermis, have been provided. Copyright (c) 2006 ISUOG.