Search

Objectives: To analyze the influence of examiners and their experience on the quality of biometric measurements via the evolution of z scores in a longitudinal multicenter study., Methods: This retrospective study included 4607 sonographic fetal biometric examinations performed by 18 examiners at the beginning of their sonography training. To analyze the quality of biometric measurements, z scores comparing the individual measurements with the expected values from a standard population were computed. To investigate the effect of examiners and their experience, we applied a multivariable regression analysis via generalized additive mixed models., Results: Mean z scores for biparietal diameter, abdominal circumference, and femur length were statistically different from the expected value of 0 (P < .001); no significant differences were found for head circumference measurements. Regression analyses showed a significant effect of the number of examinations on the distribution of z scores for each type of measurement. This effect yielded z score values close to the expected value of 0 at 100 to 200 examinations for all biometric measurements, indicating good consistency with the distribution of values in the reference population. Near the end of the study period, an increasing tendency toward either overestimation (head circumference) or underestimation (biparietal diameter, abdominal circumference, and femur length) was observed., Conclusions: A longitudinal analysis of the z score distribution for quality control of biometry is feasible. A prospective and automatized use of this technique could help identify potential systematic errors and therefore improve the detection rate for high-risk pregnancies., (© 2017 by the American Institute of Ultrasound in Medicine.)

Objectives: To evaluate the influence of examiner experience on the accuracy of sonographic weight estimation and to further analyze examiners' individual learning curves., Methods: In this multicenter study, 4613 sonographic weight estimations performed by 18 examiners at the beginning of their ultrasound training were included. To assess the effect of experience on the accuracy of weight estimation, a multivariable mixed regression model analysis was performed, with percentage error and absolute percentage error as outcome variables and the examiner, the examiner's experience (number of examinations), birth weight, gestational age, scan-to-delivery interval, and maternal body mass index as fixed effects and the perinatal center as random intercepts. To further analyze the individual learning curves of the examiners, the cumulative summation technique was used., Results: Regression analyses showed a significant influence of the number of examinations on the accuracy of sonographic weight estimation after adjustment for the above-mentioned parameters (P < .001). A typical learning curve with improving accuracy was found until approximately 200 examinations. Between 200 and 300 examinations, the diagnostic performance started to deteriorate again, with a continuous decrease until the end of the study period. Cumulative summation charts representing individual learning curves varied greatly between different examiners., Conclusions: These findings indicate the great importance of continuous quality control systems in sonographic weight estimation., (© 2016 by the American Institute of Ultrasound in Medicine.)

Introduction: To evaluate the influence of the time interval between examination and delivery on the accuracy of sonographic fetal weight estimation (WE)., Materials and Methods: 8723 singleton pregnancies were included in this retrospective cohort study. Fetuses were divided into eight groups with regard to the time interval between estimation and delivery (group 1: 0 days; group 2: 1-3 days; group 3: 4-7 days; group 4: 8-14 days; group 5: 15-21 days; group 6: 22-28 days; group 7: 29-35 days; group 8: 36-42 days). The accuracy of WE was compared between the different time interval groups and five commonly used formulas using means of percentage errors (MPE), medians of absolute percentage errors, and proportions of estimates within 10 % of actual birth weight., Results: In group one, the Hadlock I and Warsof formula showed a systematic underestimation of fetal weight (negative MPEs). No systematic error was found with the Hadlock II formula and the equations of Merz and Shepard showed a systematic overestimation (positive MPEs). MPE values of the Hadlock I, II and Warsof formulas were closest to zero in WEs of group two. From group three to six, MPE values decreased continuously. With the Merz and Shepard equations MPEs were closest to zero in group four., Discussion: The best accuracy of sonographic WE with most of the commonly used equations is achieved within a scan-to-delivery interval of 1 week.

Objectives: The purpose of this study was to develop a new specific weight estimation formula for small-for-gestational-age (SGA) fetuses that differentiated between symmetric and asymmetric growth patterns., Methods: A statistical estimation technique known as component-wise gradient boosting was applied to a group of 898 SGA fetuses (symmetric, n = 750; asymmetric, n = 148). A new formula was derived from the data obtained and was then compared to other commonly used equations., Results: The new formula derived is as follows: estimated fetal weight = e^[1.3734627 + 0.0057133 × biparietal diameter + 0.0011282 × head circumference + 0.0201147 × abdominal circumference + 0.0183081 × femur length - 0.0000177 × biparietal diameter(2) - 0.0000018 × head circumference(2) - 0.0000297 × abdominal circumference(2) -0.0001007 × femur length(2) + 0.0397563 × I(sex = male) + 0.0064505 × gestational age (days) + 0.0096528 × I(SGA = asymmetric)], where the function I denotes an indicator function, which is 1 if the expression is fulfilled (sex = male; SGA type = asymmetric) and otherwise 0. In the whole study group and the 2 subgroups, the new formula showed the lowest median absolute percentage error, mean percentage error, and random error and the best distribution of absolute percentage errors within prespecified error bounds., Conclusions: The new formula substantially improves weight estimation in SGA fetuses.

Objective: To determine whether the amniotic fluid index (AFI) or the single deepest vertical pocket (SDP) technique for estimating amniotic fluid volume is superior for predicting adverse pregnancy outcome., Methods: This was a multicenter randomized controlled trial including 1052 pregnant women with a term singleton pregnancy across four hospitals in Germany. Women were assigned randomly, according to a computer-generated allocation sequence, to AFI or SDP measurement for estimation of amniotic fluid volume. Oligohydramnios was defined as AFI ≤ 5 cm or the absence of a pocket measuring at least 2 × 1 cm. The diagnosis of oligohydramnios was followed by labor induction. The primary outcome measure was postpartum admission to a neonatal intensive care unit. Further outcome parameters were the rates of diagnosis of oligohydramnios and induction of labor (for oligohydramnios or without specific indication), and mode of delivery., Results: Postpartum admission to a neonatal intensive care unit was similar between groups (4.2% (n = 21) vs 5.0% (n = 25); relative risk (RR), 0.85 (95% CI, 0.48-1.50); P = 0.57). In the AFI group, there were more cases of oligohydramnios (9.8% (n = 49) vs 2.2% (n = 11); RR, 4.51 (95% CI, 2.2-8.57); P < 0.01) and more cases of labor induction for oligohydramnios (12.7% (n = 33) vs 3.6% (n = 10); RR, 3.50 (95% CI, 1.76-6.96); P < 0.01) than in the SDP group. Moreover, an abnormal cardiotocography was seen more often in the AFI group than in the SDP group (32.3% (n = 161) vs 26.2% (n = 132); RR, 1.23 (95% CI, 1.02-1.50); P = 0.03). The other outcome measures were not significantly different between the two groups., Conclusions: Use of the AFI method increased the rate of diagnosis of oligohydramnios and labor induction for oligohydramnios without improving perinatal outcome. The SDP method is therefore the favorable method to estimate amniotic fluid volume, especially in a population with many low-risk pregnancies. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd., (Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.)

Purpose: To evaluate the accuracy of intrapartum sonographic weight estimation (WE)., Materials and Methods: This retrospective, cross-sectional study included 1958 singleton pregnancies. Inclusion criteria were singleton pregnancy with cephalic presentation, vaginal delivery and ultrasound examination with complete biometric parameters performed on the day of delivery during the latent or active phase of labor, and absence of chromosomal or structural anomalies. The accuracy of intrapartum WE was compared to a control group of fetuses delivered by primary cesarean section at our perinatal center and an ultrasound examination with complete biometric parameters performed within 3 days before delivery (n = 392). Otherwise, the same inclusion criteria as in the study group were applied. The accuracy of WE was compared between five commonly applied formulas using means of percentage errors (MPE), medians of absolute percentage errors (MAPE), and proportions of estimates within 10 % of actual birth weight., Results: In the whole study group, all equations showed a systematic underestimation of fetal weight (negative MPEs). Overall, best MAPE and MPE values were found with the Hadlock II formula, using BPD, AC and FL as biometric parameters (Hadlock II, MPE: -1.28; MAPE: 6.52). MPEs differed significantly between WE in the study and control group for all evaluated formulas: in the control group, either no systematic error (Hadlock III, IV and V) or a significant overestimation (Hadlock I, II) was found. Regarding MAPEs, application of the Hadlock III (HC, AC, FL) and V (AC) formula resulted in significant lower values in the control group (Hadlock III, MAPE: 7.48 vs. 5.95, p = 0.0008 and Hadlock V, MAPE: 8.79 vs. 7.52, p = 0.0085). No significant differences were found for the other equations., Conclusions: A systematic underestimation of fetal weight has to be taken into account in sonographic WE performed intrapartum. Overall, the best results can be achieved with WE formulas using the BPD as the only head measurement.

Purpose: To evaluate the influence of the time interval between examination and delivery on the accuracy of sonographic weight estimation (WE) in fetal macrosomia., Materials and Methods: 896 singleton pregnancies (birth weight > 4,000 g) with a total of 1,281 sonographic weight estimations were included in this retrospective cohort study. Fetuses were divided into six groups with regard to the time interval between estimation and delivery: group 1: scan-to-delivery interval: 0 days; group 2: scan-to-delivery interval: 1-3 days; group 3: scan-to-delivery interval: 4-7 days; group 4: scan-to-delivery interval: 8-14 days; group 5: scan-to-delivery interval: 15-21 days; group 6: scan-to-delivery interval: 22-42 days. The accuracy of WE was compared between five commonly used formulas using means of percentage errors (MPE), random error, medians of absolute percentage errors (MAPE), and proportions of estimates within 10 % of actual birth weight., Results: Significant differences were found between the time interval groups with regard to MAPE and MPE values (p < 0.001). All formulas showed a systematic underestimation of fetal weight (negative MPEs) (p < 0.05). MPE values were closest to zero in time interval group 1 and 2. From group 3 to 6, a continuous decrease was observed. The lowest MAPE was found with the Merz formula in group 1 and 2. Values increased continuously from group 3 to 6. Differences between time interval group one and three did not reach statistical significance., Conclusions: WE in fetal macrosomia shows the best results when examinations are performed within 7 days before delivery, using the formula of Merz et al. Accuracy significantly decreases after this time period.

Purpose: The accuracy of the sonographic weight estimation (WE) of fetuses with congenital diaphragmatic hernia (CDH) is significantly lower than that of fetuses without any malformations. The objective of this study was to develop and evaluate the first specific sonographic weight formula for fetuses with CDH., Materials and Methods: In a retrospective, multicenter, cohort study, a statistical estimation technique known as "multivariable fractional polynomial regression" was applied to a group of 146 fetuses with CDH. Each fetus underwent an ultrasound examination with complete biometric parameters within 7 days of delivery. A new formula was derived using the obtained data and was then compared with other commonly used equations. The accuracy of the different formulas was compared using means of signed percentage errors (SPE), medians of absolute percentage errors (MAPE), and fractions of estimates within prespecified error bounds., Results: The new derived formula is: EFW = 10^(4.6729 107 371 + 0.2365 011 768 * HC + 0.2228 897 682 * FL^2 - 0.0129 895 773 * FL^3 - 1.0470 039 072 * (FL * HC)^0.5 + 0.0004 314 661 * (AC * HC) - [in case of liver herniation] 0.0062 112 122), where EFW is the estimated fetal weight, HC is the head circumference, AC is the abdominal circumference, and FL is the femur length. The new formula proved to be superior to other established equations, showing both the lowest median absolute percentage error (MAE: 6.97) and mean signed percentage error (SPE: 0.40), and the best distribution of absolute percentage errors within prespecified error bounds., Conclusion: This new formula significantly improves weight estimation in fetuses with CDH., (© Georg Thieme Verlag KG Stuttgart · New York.)