Assessment Of Fetal Adrenal Gland Volume Using Three-dimensional Ultrasound

Objective:To assess the normal fetal adrenal gland volume during normal gestation and its change in high-risk pregnancy.Methods:We performed our study on 402 normal fetuses with gestational age ranging from 21 to 40 weeks and 16 cases of PROM,6 cases of ICP,8 cases of FGR-suspected using a 3-D ultrasound volume scanner with a pure cross-sectional design and the measurement of common fetal growth indices.Using the rotational technique with the VOCAL-imaging program(Virtual Organ Computer-aided Analysis) and through the predefined rotations of 30⁰.Correlation analysis was calculated to determine the coeficient of correlation of the fetal adrenal gland volume vs.gestational age(GA).Applying regression analysis to find the best-fit regression model and establish best-fit equations to obtain the predicted values of fetal adrenal gland volume respectively using GA as the independent variable.Then the goodness of fit of the regression model was assessed.To establish the chart of the normal reference centiles of fetal adrenal gland volume,the age-related reference centiles were calculated using the regression equation.In addition,correlation and regression analysis were calculated to find the relationship between the common fetal growth indices as well as EFW derived from Hadlock's equation and the volume of fetal adrenal gland volume respectively.To assess intraobserver and interobserver reproducibility of volume measurements,some 3-D datasets of fetal adrenal gland were measured ten times consecutively by the same observer or two observers at random.Meanwhile,fetal adrenal gland volume in the status of PROM,ICP or FGR is also measured by 3-D dimensional ultrasound.Fetal adrenal gland volume in PROM,ICP,or FGR is compared with that in normal fetuses using univariate general linear analysis model.Results:Paired t test showed no statistical significance for the intraobserver reproducibility or in the interobserve reproducibility.Our results showed that fetal adrenal gland volume is highly correlated with GA.Furthermore,by the natural logarithmic transformation of the adrenal gland volume and GA,the best-fit equation was transformed into linear regression equation of which the residual showed homogeneity of variance and normal distribution.Following the theory of normal distribution,the age-related reference centiles was calculated and a normal growth chart of fetal adrenal gland volume was established for clinical reference using GA as the independent variable and adrenal gland volume as the dependent variable,the best-fit regression equation was In(left adrenal gland volume(10^-3mL))=-10.998 +4.8191n(GA)(r=0.974,p＜0.01) and ln(right adrenal gland volume(10^-3mL))= -8.363+4.1371n(GA)(r=0.969,p＜0.01).In addition,the fetal adrenal gland volume in normal gestation was also correlated with the common fetal growth indices and EFW (all p＜0.01).Corrected by GA,in PROM,the fetal adrenal gland volume is statistically larger than that in normal fetus.While the fetal adrenal gland volume in the status of ICP or FGR is statistically smaller than that in normal fetus.Corrected by GA and expected fetal weight,in FGR,fetal right adrenal gland volume is still statically lower than that in normal fetus.Conclusion:Our research established a normal growth chart of fetal adrenal gland volume for clinical reference.In the status of PROM,ICP or FGR,fetal adrenal gland volume assessed by 3-D US is statistically different from that of normal fetus.