Correlation of Fractional Limb Volume Measurements with Neonatal Morphometric Indices.

OBJECTIVES: Fractional thigh volume (TVol) and fractional arm volume (AVol) measurements by three-dimensional (3D) ultrasound can reveal valuable information on fetal soft tissue development. However, it is not clear whether TVol or AVol provides better estimates of fetal body proportion and adiposity, independent of routine two-dimensional (2D) ultrasound biometry. The primary objective of the current study was to determine the correlations between fractional limb volumes (FLVs) and neonatal anthropometric parameters. DESIGN: In this cross-sectional study, fetal FLVs were obtained within 24 h before term delivery from 40 medically and obstetrically uncomplicated pregnancies scheduled for elective cesarean section. TVol and AVol were determined using offline software. Postnatal morphometric data including birth weight; crown-heel, arm, and leg lengths; head, abdominal, mid-thigh, and mid-arm circumferences; and anterior thigh, biceps, and subscapular skinfold thicknesses were obtained. Pearson and partial correlation analyses were used to determine the relationships across antenatal volume calculations and neonatal indices. Correlation coefficients (r) were calculated. RESULTS: Mean maternal age, BMI, and parity were 29.1 ± 5.4 years, 29.7 ± 3.5 kg/m2, and 1.0 ± 1.3, respectively. AVol showed moderate correlations with most of the neonatal parameters, including mid-thigh circumference (r = 0.683), mid-arm circumference (r = 0.627), birth weight (r = 0.583), head circumference (HC, r = 0.560), and abdominal circumference (r = 0.542). However, TVol was weakly related to only some of the indices. After controlling for gestational age, maternal age, BMI, parity, and 2D ultrasound biometry, TVol was no longer associated with any of the parameters, while AVol was independently correlated with mid-thigh (r = 0.724) and mid-arm circumference (r = 0.560), birth weight (r = 0.502), ponderal index (r = 0.402), HC (r = 0.382), biceps (r = 0.384), and subscapular skinfold thickness (r = 0.350). LIMITATIONS: The current design includes limited number of pregnancies with only scheduled cesarean deliveries. Neonatal percent body fat was not calculated, and air-displacement plethysmography was not used to assess neonatal body composition. The study population was Caucasian with a relatively high maternal BMI, which may limit extrapolation of the results to other settings. CONCLUSIONS: AVoL measurements by 3D ultrasound before delivery are significantly correlated with most of the neonatal morphometric indices, independent of maternal characteristics and 2D biometric parameters. AVol may have advantages over TVol for assessing limb soft tissue development in term fetuses. Future research can focus on feasibility and predictive ability of AVol measurements in prospective studies that include serial biometry over time.

Differences in fetal fractional limb volume changes in normal and gestational diabetic pregnancies: an exploratory observational study.

OBJECTIVE: Fetal fractional limb volume has been proposed as a useful measure for quantifying fetal soft tissue development. The aim of this study was to investigate the growth of fractional arm volume (AVol) and fractional thigh volume (TVol) of fetuses with maternal gestational diabetes (GDM) compared with those of fetuses with normal glucose tolerance (NGT). We hypothesised fetal fractional limb volume would be larger in the GDM group than in the NGT group in late gestation. DESIGN: Exploratory observational study. SETTING: Saitama Municipal Hospital. SAMPLE: A total of 165 (125 NGT and 40 GDM) singleton Japanese pregnant women. METHODS: AVol and TVol were assessed between 20 and 37 weeks' gestation as cylindrical limb volumes based on 50% of the fetal humeral or femoral diaphysis length. Women were diagnosed as GDM based on the criteria of the Japan Society of Obstetrics and Gynecology. MAIN OUTCOME MEASURES: AVol and TVol were compared between women with NGT and those with GDM at each gestational age period (2-week intervals from 20 to 37 weeks' gestation). RESULTS: Overall, 287 ultrasound scans were performed (NGT group, 205 scans; GDM group, 82 scans). There was no significant difference of AVol between the groups before 32 weeks' gestation. AVol was significantly larger in the GDM group than in the NGT group after 32 weeks' gestation (P < 0.05). TVol was not statistically different between the groups across gestation. CONCLUSIONS: Detection of variations in fetal AVol may provide greater insight into understanding the origins of altered fetal body proportion in GDM. TWEETABLE ABSTRACT: AVol, but not TVol, is significantly larger in fetuses with GDM than in those with NGT after 32 weeks' gestation.

Two-dimensional fetal biometry versus three-dimensional fractional thigh volume for ultrasonographic prediction of birthweight.

OBJECTIVE: To develop and validate birthweight prediction models using fetal fractional thigh volume (TVol) in an Indian population, comparing them with existing prediction models developed for other ethnicities. METHODS: A prospective observational study was conducted among 131 pregnant women (>36 weeks) attending a tertiary hospital in New Delhi, India, for prenatal care between December 1, 2014, and November 1, 2016. Participants were randomly divided into formulating (n=100) and validation (n=31) groups. Multiple regression analysis was performed to generate four models to predict birthweight using various combinations of two-dimensional (2D) ultrasonographic parameters and a three-dimensional (3D) ultrasonographic parameter (TVol). The best fit model was compared with previously published 2D and 3D models. RESULTS: The best fit model comprised biparietal diameter, head circumference, abdominal circumference, and TVol. This model had the lowest mean percentage error (0.624 ± 8.075) and the highest coefficient of determination (R2 =0.660). It correctly predicted 70.2% and 91.6% of birthweights within 5% and 10% of actual weight, respectively. Compared with previous models, attributability for the 2D and 3D models was 0.65 and 0.55, respectively. Accuracy was -0.05 ± 1.007 and -2.54 ± 1.11, respectively. CONCLUSION: Models that included TVol provided good prediction of birthweight in the target population.

A Novel Semiautomated Fractional Limb Volume Tool for Rapid and Reproducible Fetal Soft Tissue Assessment.

The purpose of this study was to document the reproducibility and efficiency of a semiautomated image analysis tool that rapidly provides fetal fractional limb volume measurements. Fifty pregnant women underwent 3-dimensional sonographic examinations for fractional arm and thigh volumes at a mean menstrual age of 31.3 weeks. Manual and semiautomated fractional limb volume measurements were calculated, with the semiautomated measurements calculated by novel software (5D Limb Vol; Samsung Medison, Seoul, Korea). The software applies an image transformation method based on the major axis length, minor axis length, and limb center coordinates. A transformed image is used to perform a global optimization technique for determination of an optimal limb soft tissue boundary. Bland-Altman analysis defined bias with 95% limits of agreement (LOA) between methods, and timing differences between manual versus automated methods were compared by a paired t test. Bland-Altman analysis indicated an acceptable bias with 95% LOA between the manual and semiautomated methods: mean arm volume ± SD, 1.7% ± 4.6% (95% LOA, -7.3% to 10.7%); and mean thigh volume, 0.0% ± 3.8% (95% LOA, -7.5% to 7.5%). The computer-assisted software completed measurements about 5 times faster compared to manual tracings. In conclusion, semiautomated fractional limb volume measurements are significantly faster to calculate when compared to a manual procedure. These results are reproducible and are likely to reduce operator dependency. The addition of computer-assisted fractional limb volume to standard biometry may improve the precision of estimated fetal weight by adding a soft tissue component to the weight estimation process.

Comparison of 2- and 3-Dimensional Sonography for Estimation of Birth Weight and Neonatal Adiposity in the Setting of Suspected Fetal Macrosomia.

OBJECTIVES: To compare the accuracy of 2-dimensional (2D) and 3-dimensional (3D) fetal measurements for prediction of birth weight Z score and neonatal adiposity (percent body fat) in the setting of suspected fetal macrosomia. METHODS: We conducted a prospective observational study of term singleton pregnancies with suspected macrosomia. Patients were enrolled on admission to labor and delivery and underwent sonographic examinations. Within 48 hours of delivery, neonatal anthropometric measurements were obtained. RESULTS: Thirty-four neonates were included in the analysis. Mothers were very obese (mean body mass index ± SD, 39.1 ± 7.8 kg/m(2)); 56.5% were white; and 39.1% had diabetes. Neonates were 38% female and had a mean birth weight of 3940.0 ± 496.8 g, percent body fat of 18.5% ± 4.0%, and Ponderal index of 2.8 ± 0.3 g/cm(3). Mean 2D estimated fetal weight was 3973 ± 443 g; mean 3D estimated fetal weight was 3803 ± 528 g; and mean thigh volume was 102.5 ± 19.6 cm(3). Both 2D and 3D measurements accounted for about half the variance in predicted birth weight (R(2) for 2D = 0.53, 71% within 10% of birth weight; R(2) for 3D = 0.47, 65% within 10% of birth weight). Thigh volume Z score was the prenatal parameter most highly correlated with both birth weight Z score (R(2) = 0.52; r = 0.72; 95% confidence interval, 0.54-0.84; P < .001) and percent body fat (R(2) = 0.22; r = 0.47; 95% confidence interval, 0.17-0.69; P = .04). CONCLUSIONS: In our population of fetuses with suspected macrosomia, fractional thigh volume was the best sonographic estimate of neonatal percent body fat and birth weight Z score. Future research on prediction of neonatal weight and adiposity in macrosomic fetuses should include an estimate of fetal soft tissue given the generalized increase in body fat of these fetuses.

Three-dimensional ultrasound using the VOCAL technique for estimation of reference values of fetal thigh volume in normally grown Egyptian fetuses from 20 to 41 weeks.

OBJECTIVE: To establish the normal reference values for the fetal thigh volume (FTV) of normally grown Egyptian fetuses using three-dimensional (3D) virtual organ computer aided analysis (VOCAL) method. PATIENTS AND METHODS: A total of 334 Egyptian pregnant women carrying a singleton living normally grown fetus between the 20th and the 41st weeks of gestation were enrolled in this cross-sectional study. FTV was measured using the 3D VOCAL method with 30° rotation. Estimated fetal weight (EFW) was calculated based on Hadlock formula. RESULTS: FTV correlated strongly with gestational age (r = 0.921, p < 0.001) and EFW (r = 0.891, p < 0.001). For clinical application, a nomogram of growth percentiles of FTV was produced. CONCLUSION: Reference values of FTV between 20th and 41st weeks of gestation in normally grown Egyptian fetuses were provided using the 3D VOCAL method. These data may be helpful to assess fetal growth and to diagnose deviation from normal.

Fetal Development of the Human Obturator Internus Muscle With Special Reference to the Tendon and Pulley.

To examine the development of the tendon pulley of the obturator internus muscle (OI), we observed paraffin sections of 26 human embryos and fetuses (∼6-15 weeks of gestation). The OI was characterized by early maturation of the proximal tendon in contrast to the delayed development of the distal tendon. At 6 weeks, the ischium corresponded to a simple round mass similar to the tuberosity in adults. At 8 weeks, before development of the definite lesser notch of the ischium, initial muscle fibers of the OI, running along the antero-posterior axis, converged onto a thick and tight but short tendon running along the left-right axis. Thus, at the beginning of development, the OI muscle belly and tendon met almost at a right angle. At 10 weeks, the OI tendon extended inferiorly along the sciatic nerve, but the distal part remained thin and loose and it was embedded in the gluteus medius tendon. At 15 weeks, in association with the gemellus muscles, the distal OI tendon was established. The mechanically strong sciatic nerve was first likely to catch the OI muscle fibers to provide a temporary insertion. Next, the ischium developing upward seemed to push the tendon to make the turn more acute along the cartilaginous ridge. Finally, the gemellus muscle appeared to provide inferior traction to the OI tendon for separation from the gluteus medius to create the final, independent insertion. Without such guidance, the piriformis tendon first attached to the OI tendon and then merged with the gluteus medius tendon.

[Correlation between ultrasonographic measurement of fetal thigh soft-tissue thickness and selected fetal ultrasonographic and maternal anthropometric parameters]. / Ocena korelacji ultrasonograficznego pomiaru tkanek miekkich uda plodu z jego wybranymi parametrami sonograficznymi i antropometrycznymi ciezarnych.

AIM: The aim of the study was to assess a correlation between ultrasonographic measurement of fetal thigh soft-tissue thickness (FTSTT) and selected fetal ultrasonographic and maternal anthropometric parameters. MATERIAL AND METHODS: A total of 140 women with a singleton term pregnancy were included in the study Anthropometric maternal and fetal measurements were assessed. Fetal weight was estimated with the Hadlock formula using head circumference (HC), abdomen circumference (AC), biparietal diameter (BPD), and femoral length (FL). FTSTT was measured using the method of Scioscia M. et al. Then, statistical analysis of the correlation between FTSTT and maternal anthropometric and fetal ultrasonographic parameters was performed. RESULTS: A statistically significant correlation was found between ultrasonographically estimated fetal weight and BPD, HC, AC, FL and FTSTT, as well as between FTSTT and neonatal birthweight and length, and maternal pre-pregnancy and pre-delivery weight. This correlation was not found between FTSTT and maternal BMI and weight gain during pregnancy A statistically significant correlation was detected between FTSTT and neonatal birthweight of newborns born between 38 and 40 weeks of gestation but no such correlation was found at 37 and 41 weeks of gestation. In addition, no statistically significant difference was observed in the measurement of FTSTT between physiological pregnancies and those complicated by diabetes. FTSTT measurements in fetuses with macrosomia (real and determined on the basis of ultrasound examination) were not statistically different from those of fetuses without macrosomia. CONCLUSIONS: FTSTT measurement may be helpful in estimating fetal weight, but it is not useful in the diagnosis of fetal macrosomia.

Estimation of birthweight by measurement of fetal thigh soft-tissue thickness improves the detection of macrosomic fetuses.

The accuracy of sonographic estimation of birthweight in suspected macrosomic fetuses is compromised by the imprecision of the biometrical measurements. This prospective study evaluated the performance of an equation based on linear measurement of the soft tissue above the external side of the fetal femur. The performance of this algorithm was compared with two classical algorithms. Sonographic measurements were taken within 48 h before of delivery. Sixty-two patients with fetuses with suspected macrosomia were enrolled. The studied formulas were compared between them and showed a significant correlation with birthweight (p < 0.0001) and satisfactory statistical performances (r > 0.9). The new formula showed a reduced standard deviation that means a lower internal error in the prediction. This study supports the potential of this new approach for the estimation of birthweight in large fetuses based on sonographic linear measurements only.

Fetal mid-thigh soft-tissue thickness: a novel method for fetal weight estimation.

PURPOSE: To derive a novel formula for fetal weight estimation utilizing the linear measurement of mid-thigh soft-tissue thickness (STT). METHODS: 300 women, with singleton uncomplicated pregnancy, were included in a prospective cross-sectional study. The study included four consecutive phases: phase (1) validated the original Scioscia's formula, phase (2) derived a novel modified formula for fetal weight estimation, phase (3) validated the novel modified formula, and phase (4) evaluated the agreement between the modified and original formulae. RESULTS: A statistically significant correlation was found between actual fetal weight (AFW) and various sonographic biometric measurements including mid-thigh STT (r (2) = 0.656, p < 0.001), femur length (FL) (r (2) = 0.573, p < 0.001), bi-parietal diameter (BPD) (r (2) = 0.250, p < 0.001), abdominal circumference (AC) (r (2) = 0.310, p < 0.001), and estimated fetal weight (EFW) using the original Scioscia's formula (r (2) = 0.644, p < 0.001). The modified formula showed a better signed % difference (median = -0.41 %, IQR -1.88 to 2.03) than the original formula (median = -0.51 %, IQR -2.33 to 2.00). It was noted that, using the original formula, 88.7 % of the sample had absolute error below 5 and 98.3 % of the sample had absolute error below 10 %. On the other hand, using the modified formula, 87.3 % of the sample had absolute error below 5 %, while 97.3 % had absolute error below 10 %. The agreement between the two formulae was moderate as 134 patients out of 150 had similar ranking (κ = 0.57). CONCLUSION: Fetal mid-thigh SST is a simple, useful, and easily applicable parameter for fetal weight estimation.

Fetal weight estimation in gestational diabetic pregnancies: comparison between conventional and three-dimensional fractional thigh volume methods using gestation-adjusted projection.

OBJECTIVES: To evaluate the accuracy of gestation-adjusted birth-weight estimation using a three-dimensional (3D) fractional thigh volume (TVol) method in pregnant women with gestational diabetes mellitus (GDM), and to compare it with the conventional two-dimensional method of Hadlock et al. METHODS: Pregnant women with GDM were referred at 34 to 36 + 6 weeks' gestation for ultrasound examination. Estimated fetal weight (EFW) was obtained using both the Hadlock and the TVol methods. Using a gestation-adjusted projection method, predicted birth weight was compared to actual birth weight at delivery. RESULTS: Based on 125 pregnancies, the TVol method with gestation-adjusted projection had a mean (± SD) percentage error in estimating birth weight of -0.01 ± 5.0 (95% CI, -0.96 to 0.98)% while the method of Hadlock with gestation-adjusted projection had an error of 1.28 ± 9.1 (95% CI, -0.33 to 2.87)%. The mean percentage error of the two methods was significantly different (P = 0.039), while the random error was not (P = 1.0). For the prediction of macrosomia (birth weight ≥ 4000 g, n = 19), sensitivity was 84 and 63% for the TVol and Hadlock methods, respectively (95% CI for difference -2 to 44%, P = 0.22) and specificity was 96 and 89% for the TVol and Hadlock methods, respectively (95% CI for difference 5-9%, P = 0.01). CONCLUSIONS: In women with GDM, a new method of estimating birth weight based on 3D-TVol measurements performed at 34 + 0 to 36 + 6 weeks' gestation and gestation-adjusted projection of estimated fetal weight, is more accurate than the standard method based on Hadlock's formula in predicting birth weight. The TVol method has comparable sensitivity but higher specificity than the Hadlock method in predicting neonatal macrosomia.

Prediction of macrosomia by serial sonographic measurements of fetal soft-tissues and the liver in women with pregestational diabetes.

OBJECTIVES: This study aimed to determine whether antenatal ultrasound measurements of fetal soft-tissues and liver can predict macrosomia in women with pregestational diabetes. METHODS: Fetal biometry, soft-tissue thickness (anterior abdominal wall [STAW], thigh [STT], upper arm [STA], scapular [STS]) and liver size were measured sonographically at 23, 28, 31 and 34 weeks of gestation. Large for gestational age (LGA) was defined as a birth weight greater than 90th percentile for gestational age on standard curves adjusted for maternal height and weight, parity and fetal gender. The area (±standard error) under receiver operating characteristic (AUROC) curves were also calculated. RESULTS: A total of 29 pregnant women with pregestational diabetes were included, and a total of 663 measurements taken. Fifteen neonates were LGA. There was no significant difference in fetal soft-tissue thickness at 23, 28 and 31 weeks between the LGA and non-LGA neonates. In contrast, at 34 weeks, fetal soft-tissues were significantly thicker in LGA neonates (P<0.05), but with no difference in liver surface area between the two groups. The specificity and sensitivity of 34-week ultrasonography to detect macrosomia was 78.6% and 66.7%, respectively, for abdominal circumference (AC), 71.4% and 93.3% for STT, 85.7% and 80.0% for STA, and 71.4% and 86.7% for STAW. No parameter was more powerful than the others. The best AUROC curves were found for AC (0.807), STT (0.821), STA (0.855) and STAW (0.821). CONCLUSION: Third-trimester sonographic measurements of fetal soft-tissue may help to detect macrosomia in pregnancies complicated by pregestational diabetes.

Prospective validation of fetal weight estimation using fractional limb volume.

OBJECTIVES: To prospectively validate the use of fractional limb volume measurements for estimated fetal weight (EFW) during the second and third trimesters of pregnancy and to summarize the medical literature regarding application of fractional limb volume for fetal weight estimation. METHODS: One hundred and sixty-four women prospectively underwent three-dimensional ultrasonography within 4 days of delivery. Birth weights (BWs) ranged from 390 to 5426 g. Fetal measurements were extracted using volume datasets for biparietal diameter, abdominal circumference, femur diaphysis length, fractional arm volume and fractional thigh volume. Fractional limb volumes were manually traced from a central portion of the humerus or femur diaphysis. Mean percentage differences and SDs of the percentage differences were calculated for EFW. The proportion of newborns with EFW within 5 or 10% of BW were compared with an estimate obtained using a Hadlock formula that was modified using model coefficients from the same local population sample. RESULTS: Ultrasound scans were performed between 21.7 and 42 weeks' menstrual age. Optimal model performance (1.9 ± 6.6%) resulted from using a combination of biparietal diameter, abdominal circumference and fractional thigh volume. The precision of this model was superior to results obtained using a modified Hadlock model (1.1 ± 8.4%), although accuracy of these predictions was slightly decreased for female infants. For all fetuses, the prediction model that incorporated fractional thigh volume correctly classified a greater proportion of EFW within 5% (55.1 vs 43.7%; P = 0.03) or 10% (86.5 vs 75.9%; P < 0.05) of BW when compared with the modified Hadlock model. CONCLUSIONS: Fractional thigh volume can be added to two-dimensional sonographic measurements of the head and trunk to improve the precision of fetal weight estimation. This approach permits the inclusion of soft tissue development as part of a weight estimation procedure for the assessment of generalized fetal nutritional status.

Fetal thigh and upper arm volumes by 3D-sonography: comparison between multiplanar and XI VOCAL methods.

OBJECTIVE: To compare fetal upper arm and thigh volume measurements acquired by three-dimensional (3D) ultrasound using the multiplanar and the eXtended Imaging Virtual Organ Computer-aided AnaLysis (XI VOCAL) methods with different number of sectional planes. METHODS: This study enrolled 40 healthy pregnant women between 20 and 40 weeks of gestation. The volume of fetal limbs was calculated using the multiplanar (with 5.0 mm intervals) and the XI VOCAL (with 5, 10, 15, and 20 slice planes) methods. Comparison between the techniques was made by analysis of variance and Bonferroni statistical tests. RESULTS: Mean fetal upper arm volume measured by the 15 sectional planes XI VOCAL method was lower than the same method using 5 and 10 planes instead (p = 0.025 and 0.039, respectively). Fetal thigh volume showed no statistically significant differences among all studied methods. CONCLUSION: The XI VOCAL using 15 sectional planes method underestimated the fetal upper arm volume by 5 and 10 planes XI VOCAL techniques.

Influence of maternal glycemia on intrauterine fetal adiposity distribution after a normal oral glucose tolerance test at 28 weeks gestation.

OBJECTIVE: To examine the relationship between maternal glucose levels and intrauterine fetal adiposity distribution in women with a normal oral glucose tolerance test (OGTT) at 28 weeks gestation. STUDY DESIGN: We recruited 231 women with a singleton pregnancy. At 28 and 37 weeks gestation, sonographic measurements of fetal body composition were performed. Multiple regression analysis was used to study the influence of different maternal variables on fetal adiposity distribution. RESULTS: Maternal glucose levels correlated with the fetal abdominal subcutaneous tissue measurements (r = 0.2; P = 0.014) and with birth weight (r = 0.1; P = 0.04). Maternal glucose levels did not correlate with the fetal mid-thigh muscle thickness and mid-thigh subcutaneous tissue measurements. CONCLUSION: We found that in nondiabetic women maternal glucose levels not only influence fetal adiposity and birth weight, but also influence the distribution of fetal adiposity. This supports previous evidence that maternal glycemia is a key determinant of intrauterine fetal programming.

Fetal thigh volume by 3D sonography using XI VOCAL: reproducibility and reference range for Brazilian healthy fetuses between 20 and 40 weeks.

OBJECTIVE: To provide reference values for fetal thigh volume using three-dimensional (3D) ultrasound and the eXtended Imaging Virtual Organ Computer-aided AnaLysis (XI VOCAL) method. METHODS: This is a cross-sectional study that enrolled 425 healthy pregnant women between the 20(th) and 40(th) weeks of gestation. The XI VOCAL was performed along the axial cross-section in ten sequential areas for the volumetric calculations, having the proximal and distal echogenic diaphysis as references. Second-degree polynomial regression models, with the determination of percentiles, were created to evaluate the relation between the fetal thigh volume and gestational age (GA). Intraoperator and interoperator reproducibility was evaluated using intraclass correlation coefficient. RESULTS: The mean fetal thigh volume varied from 8.00 (3.90-11.90 cm(3) ) to 122.14 cm(3) (105.0-153.50 cm(3) ) at 20 and 40 weeks of gestation, respectively. Fetal thigh volume was strongly correlated with gestational age, and the reference values can be obtained by the following mathematical equation: fetal thigh volume (cm(3) ) = 68.70-7.63 × GA + 0.23 × GA(2) (R(2) = 0.946). The intraoperator and interoperator reproducibility were excellent, with an intraclass correlation coefficient = 1.000 and 0.999, respectively. CONCLUSIONS: The reference range of fetal thigh volume was determined by 3D-ultrasound using the XI VOCAL method.

Birth-weight prediction using three-dimensional sonographic fractional thigh volume at term in a Chinese population.

OBJECTIVES: To develop and validate new birth-weight prediction models in Chinese pregnant women using fractional thigh volume. METHODS: Healthy late third-trimester fetuses within 5 days of delivery were prospectively examined using two- (2D) and three- (3D) dimensional ultrasonography. Measurements were performed using 2D ultrasound for standard fetal biometry and 3D ultrasound for fractional thigh volume (TVol) and middle thigh circumference. The intraclass correlation coefficient (ICC) was used to analyze the inter- and intraobserver reliability of the 3D ultrasound measurements of 40 fetuses. Five birth-weight prediction models were developed using linear regression analysis, and these were compared with previously published models in a validation group. RESULTS: Of the 290 fetuses studied, 100 were used in the development of prediction models and 190 in the validation of prediction models. The inter- and intraobserver variability for TVol and middle thigh circumference measurements was small (all ICCs ≥ 0.95). The prediction model using TVol, femur length (FL), abdominal circumference (AC) and biparietal diameter (BPD) provided the most precise birth-weight estimation, with a random error of 4.68% and R(2) of 0.825. It correctly predicted 69.5 and 95.3% of birth weights to within 5 and 10% of actual birth weight. By comparison, the Hadlock model with standard fetal biometry (BPD, head circumference, AC and FL) gave a random error of 6.41%. The percentage of birth-weight prediction within 5 and 10% of actual birth weight was 46.3 and 82.6%, respectively. CONCLUSION: Consistent with studies on Caucasian populations, a new birth-weight prediction model based on fractional thigh volume, BPD, AC and FL, is reliable during the late third trimester in a Chinese population, and allows better prediction than does the Hadlock model.

Multidimensional standard curve for the development process of human fetuses.

The present paper considers a multidimensional view of the standard for the development process of human fetuses. An efficient method by which to find a multidimensional standard curve for the development process of human fetuses is proposed in which a logistic function with three parameters is utilized as an underlying model and a nonlinear regression method is applied. The proposed method also identifies an approximate prediction region, which can be efficiently applied to diagnose fetal malformation.

Fetal thigh volumetry by three-dimensional ultrasound: comparison between multiplanar and VOCAL techniques.

OBJECTIVES: To evaluate the agreement between multiplanar and Virtual Organ Computer-aided AnaLysis (VOCAL()) techniques for the measurement of total fetal thigh volume and to assess the repeatability and reproducibility of measurements performed using these methods; to derive birth weight-predicting models for both methods and to compare their accuracies. METHODS: This was a cross-sectional study of 150 singleton pregnancies at 30-42 weeks of gestation in which ultrasound volumes of the fetal thigh were obtained within 48 hours of delivery and measured using multiplanar and VOCAL techniques. Bland-Altman analyses were performed to determine the agreement between the two methods, and to evaluate intraobserver and interobserver variability in a subset of 40 patients. Birth weight-predicting models were derived using total fetal thigh volumes obtained using the VOCAL (ThiV) and multiplanar (ThiM) methods as independent variables. The accuracies of these formulas were compared. RESULTS: The mean percentage difference between measurements performed using the VOCAL technique and the multiplanar technique was -0.04 and the 95% limits of agreement were -8.17 and 8.09. The mean percentage difference and 95% limits of agreement between paired measurements in the assessment of intraobserver and interobserver variability were -1.10 (-7.67 to 5.47) and 0.61 (-7.68 to 8.91) for the VOCAL technique and 1.03 (-6.35 to 8.41) and -0.68 (-11.42 to 10.06) for the multiplanar method, respectively. The best-fit formulas for predicting birth weight (BW) were: BW = 1025.383 + 12.775x ThiV; and BW = 1033.286 + 12.733x ThiM. There was no significant difference between the accuracies of these formulas. CONCLUSIONS: There is good agreement between the VOCAL and multiplanar techniques for assessment of total fetal thigh volume. Measurements performed using both methods are repeatable and reproducible. For prediction of birth weight, the formulas generated in this study can be used interchangeably.

Birth-weight prediction by two- and three-dimensional ultrasound imaging.

OBJECTIVES: To compare the accuracies of birth-weight predicting models derived from two-dimensional (2D) ultrasound parameters and from total fetal thigh volumes measured by three-dimensional (3D) ultrasound imaging; and to compare the performances of these formulae with those of previously published equations. METHODS: A total of 210 patients were evaluated to create a formula-generating group (n = 150) and a prospective-validation group (n = 60). Polynomial regression analysis was performed on the first group to generate one equation based on 2D ultrasound measurements, one based on fetal thigh volume measured by the multiplanar technique (ThiM) and one based on fetal thigh volume obtained by the Virtual Organ Computer-aided AnaLysis (VOCAL()) method (ThiV). Paired-samples t-tests with Bonferroni adjustments were used to compare the performances of these equations in the formula-finding and the prospective-validation groups. The same approach was used to compare the accuracies of the new 2D and 3D formulae with those of both original and modified 2D equations from previous publications, as well as the 3D model reported by Chang et al. RESULTS: The formulae with the best fit for the prediction of birth weight were: estimated fetal weight (EFW) = - 562.824 + 11.962x AC x FDL + 0.009 x BPD(2)x AC(2) (where AC is abdominal circumference, FDL is femur diaphysis length and BPD is biparietal diameter), EFW = 1033.286 + 12.733 x ThiM, and EFW = 1025.383 + 12.775 x ThiV. For both the formula-generating and the prospective-validation groups, there were no significant differences between the accuracies of the new 2D and 3D models in the prediction of birth weight. When applied to our population, the performances of the modified and original versions of the previously published 2D equations and the performance of the original 3D formula reported by Chang et al. were all significantly worse than our models. CONCLUSIONS: We believe that the greatest sources of discrepancy in estimation of birth weight are the phenotypic differences among patients used to create each of the formulae mentioned in this study. Our data reinforce the need for customized birth-weight prediction formulae, regardless of whether 2D or 3D measurements are employed.