Accuracy Of Sonographic Weight Estimation Research Articles

The effect of fetal weight on the accuracy of sonographic weight estimation among women with diabetes

Objective The assessment of sonographic estimated fetal weight (EFW) enables identification of fetuses in the extremes of weight, thus aiding in the planning and management of peripartum care. There are conflicting reports regarding the accuracy of EFW in diabetic mothers. We aimed to study the factors associated with the accuracy of EFW at term, specifically the role of gestational and pre-gestational diabetes in this setting. Methods A retrospective study including all women carrying singleton term gestations who delivered within a week following a sonographic fetal weight estimation between 2011 and 2019. Accurate EFW was defined as within 10% of the actual birthweight. We allocated the study cohort into two groups: (1) Accurate EFW (2) inaccurate EFW. Both groups were compared in order to identify factors associated with the inaccuracy of EFW. Results Overall, 41,263 deliveries were available for evaluation, including 412 (1.0%) deliveries among women with pre-gestational diabetes and 4,735 (11.5%) among women with gestational diabetes. Of them, 7,280 (17.6%) had inaccurate EFW. Inaccurate EFW was associated with nulliparity, OR 0.82 [95% CI] (0.78–0.87), oligohydramnios, OR 0.81 [95% CI] (0.71–0.93), pregestational diabetes, OR [95% CI] 0.61 (0.50–0.79), and extremity of fetal weight; <2,500 grams–OR [95% CI] 0.37 (0.33–0.41) and >4,000 grams OR [95% CI] 0.52 (0.48–0.57). On multiple regression analysis, the following factors were independently associated with inaccurate EFW: pregestational diabetes, OR [95% CI] 0.58 (0.46–0.73), p < .001, nulliparity, OR [95% CI] 0.86 (0.82–0.91), p < .001 and higher fetal weight (for each 500 grams), OR [95% CI [1.25 (1.21–1.30), p < .001. On analysis of different weight categories, pregestational diabetes was associated with inaccurate EFW only in those with birthweight >3,500 grams, OR [95% CI] 0.37 (0.24–0.56) (p < .001). Conclusion Among pregestational diabetic women, the accuracy of sonographic EFW when assessed to be >3,500 grams is questionable. This should be taken into consideration when consulting women and planning delivery management. Synopsis Among pregestational diabetic women, the accuracy of estimated sonographic fetal weight higher than 3,500 grams is of limited accuracy.

Longitudinal Assessment of Examiner Experience and the Accuracy of Sonographic Fetal Weight Estimation at Term.

To evaluate the influence of examiner experience on the accuracy of sonographic weight estimation and to further analyze examiners' individual learning curves. 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. 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. These findings indicate the great importance of continuous quality control systems in sonographic weight estimation.

Sonographic weight estimation in small for gestational age fetuses

Purpose: To determine the accuracy of sonographic weight estimation (WE) for small for gestational age (SGA) fetuses, and to further differentiate the evaluation between fetuses being symmetric and asymmetric SGA.

Accuracy of sonographic fetal weight estimation: influence of the scan-to-delivery interval in combination with the applied weight estimation formula.

To evaluate the influence of the time interval between examination and delivery on the accuracy of sonographic fetal weight estimation (WE). 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: 0days; group 2: 1-3days; group 3: 4-7days; group 4: 8-14days; group 5: 15-21days; group 6: 22-28days; group 7: 29-35days; group 8: 36-42days). 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. 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. The best accuracy of sonographic WE with most of the commonly used equations is achieved within a scan-to-delivery interval of 1week.

Sonographic weight estimation in fetal macrosomia: influence of the time interval between estimation and delivery

To evaluate the influence of the time interval between examination and delivery on the accuracy of sonographic weight estimation (WE) in fetal macrosomia. 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. 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. 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.

Sonographic Weight Estimation in Small-for-Gestational-Age Fetuses.

To determine the accuracy of sonographic weight estimation (WE) for small-for-gestational-age (SGA) fetuses, and to further differentiate the evaluation between symmetric and asymmetric SGA fetuses. The accuracy of WE in SGA fetuses (n = 898) was evaluated using 14 sonographic models and was further differentiated between symmetric (n = 750) and asymmetric (n = 148) SGA fetuses. SGA fetuses were considered to be asymmetric with a head circumference to abdominal circumference ratio above the 95th percentile. The accuracy of the different formulas was compared using means of percentage errors (MPE), medians of absolute percentage errors (MAPE), and proportions of estimates within 10 % of actual birth weight. RESULTS for the subgroup of asymmetric SGA fetuses differed significantly from the subgroup of symmetric SGA fetuses. MPE values were closer to zero with most of the formulas in the asymmetric SGA group. Apart from the Siemer, Shepard, Merz and Warsof equations, all formulas showed an underestimation of fetal weight in asymmetric SGA fetuses. In contrast, in the symmetric SGA group, all of the formulas commonly used for fetuses in a normal weight range showed a systematic overestimation of fetal weight. Overall the best accuracy was achieved by using the Sabbagha equation (MPE 1.7 %; SD 9.0 %; MAPE: 6.0). An accurate WE in SGA fetuses is feasible using the Sabbagha formula. However, one has to be aware of the significant differences in WE between symmetric and asymmetric SGA fetuses.

Sonographic Weight Estimation in Fetuses with Congenital Diaphragmatic Hernia

To determine the accuracy of sonographic weight estimation (WE) for fetuses with congenital diaphragmatic hernia (CDH), and to assess whether certain sonographic models perform better than others in cases of CDH. In a retrospective, multicenter cohort study, the accuracy of WE in fetuses with CDH (n = 172) was evaluated using eight sonographic models and was compared with a control group of fetuses without malformations (n = 172). Each fetus underwent ultrasound examination with complete biometric parameters within 7 days of delivery. The accuracy of the different formulas was compared using means of percentage errors (MPE), medians of absolute percentage errors (MAPE), and proportions of estimates within 10 % of actual birth weight. Fetuses with CDH had a significantly lower abdominal circumference (AC) in comparison with the control group (293.6 vs. 312.0 mm, p < 0.001). All of the formulas tested in fetuses with CDH, except for the Siemer equation (the only model that does not incorporate any abdominal measurements), showed significantly lower (more negative) MPEs, larger MAPEs, and smaller proportions of estimates within 10 % of actual birth weight in comparison with the control group. The accuracy of sonographic WE in fetuses with CDH is significantly poorer than in fetuses without malformations, principally because of a larger systematic error due to artificially small AC measurements. The development of new, specific models derived from fetuses with CDH could improve the accuracy of WE for infants with this condition.

Does use of a sex‐specific model improve the accuracy of sonographic weight estimation?

To determine whether the use of a sex-specific sonographic model improves the accuracy of fetal weight estimation. New regression models (sex-independent and sex-specific) were developed, based on 1708 sonographic weight estimations performed within 3 days prior to delivery. The accuracy of these models was compared to that of several published models including two of the original Hadlock models (which incorporate the biometric indices abdominal circumference (AC), biparietal diameter (BPD), femur diaphysis length (FL) and head circumference (HC) as follows: AC-FL-BPD and AC-FL-HC, designated here as Hadlock I and Hadlock II, respectively), modified versions of the Hadlock I and II models for which coefficients were adjusted to our local cohort, sex-specific versions of the Hadlock I and II models and Schild's model (a previously published sex-specific model). The unadjusted models of Hadlock and Schild were associated with the highest systematic error (1.6-4.9%; P < 0.001) which was significantly higher for females (2.3-4.9%) compared to males (1.6-2.0%; P < 0.001). Adjustment of model coefficients to the local population decreased the systematic error (-1.4% to 1.5%) and resulted in a systematic error that was of similar magnitude (P = 0.3) but opposite in direction for male and female fetuses. The sex-specific models (adjusted or newly developed) were associated with the lowest systematic error (-0.4 to 0.5%) and were the only models for which the systematic error was similar for male and female fetuses. There were no differences in the systematic error between adjusted sex-specific versions of the Hadlock I and II models and the newly developed sex-specific models (0.0% to 0.4% vs. - 0.4% to 0.5%; P = 0.4). The random error was similar for all models and, for most of the models, was unrelated to fetal sex. The use of sex-specific models appears to improve the accuracy of fetal weight estimation, principally because the optimal set of model coefficients differs for male and female fetuses. The improved accuracy is mainly the result of a decrease in systematic error, as the random error was not affected by the use of such sex-specific models.

Accuracy of sonographic fetal weight estimation: a matter of presentation

To assess the accuracy of sonographic weight estimation for fetuses in breech presentation, and to determine whether certain sonographic models perform better than others in cases of breech presentation. This was a retrospective cohort study of all sonographic weight estimations of fetuses in breech presentation performed within 3 days prior to delivery (n = 165). The accuracy of weight estimation was evaluated using eight sonographic models and was compared with a control group of fetuses in vertex presentation matched to the study group by birth weight and fetal gender (n = 165). After exclusion of a model based on femur diaphysis length alone, which was found to be highly inaccurate, the systematic error for fetuses in breech presentation was smaller than that observed for fetuses in vertex presentation (mean of all models - 0.14% vs. 2.0%, P = 0.01). The random error was higher in cases of breech presentation (9.4-13.2% vs. 7.5-8.9%, P < 0.05), and was lower for models that are based on three to four biometric indices (9.4-9.5%) compared with models that incorporate one to two biometric indices (10.8-13.6%, P < 0.05). Overall, the higher random error outweighed the decrease in the systematic error, as reflected by the lower fraction of weight estimations within 10% of birth weight among fetuses in breech presentation. Models based on three to four biometric indices were more accurate in detecting the weight thresholds beyond which a trial of vaginal delivery is usually not recommended. Sonographic weight estimation appears to be less accurate for fetuses in breech presentation, principally because of a larger random error. The use of sonographic models that are based on three to four biometric indices, training aimed at improving measurement in breech fetuses and the development of sonographic models derived from fetuses in breech presentation, may improve the accuracy of weight estimation in these cases.

Accuracy of sonographic weight estimation as a function of fetal sex

To determine whether the accuracy of sonographic fetal weight estimation is related to fetal sex. The accuracy of sonographic fetal weight estimation was compared between male and female fetuses using 3672 sonographic weight estimations performed within 3 days prior to delivery. Fetal weight was estimated using eight regression models that are based on different combinations of the following biometric parameters: abdominal circumference (AC), femur diaphysis length (FL), biparietal diameter (BPD) and head circumference (HC). In seven out of the eight models tested, the presence of a male fetus was associated with a significantly lower systematic error compared with a female fetus (-0.2 to 2.1% vs. 1.3 to 6%, P<0.001). On multivariate analysis, fetal sex was independently associated with sonographic accuracy so that the likelihood of a weight estimation within 10% of birth weight was 30% higher for male fetuses compared with female fetuses. The biometric parameters that contributed most to these sex-related differences were FL and AC, while models that included HC were associated with the lowest differences in the systematic error between male fetuses and female fetuses. For most models, the random error and correlation between estimated weight and birth weight were not affected by fetal sex (8.1-12.8% vs. 8.2-13.6%, and 0.856-0.944 vs. 0.842-0.944, respectively). Sonographic estimation of fetal weight is more accurate for male fetuses than for female fetuses. The use of sex-specific models may improve the accuracy of fetal weight estimation for female fetuses.

Prediction of fetal weights in twins

To determine the accuracy of sonographic weight estimation of twin fetuses. In 73 twin-pregnancies, fetal weight estimation by ultrasound was performed within 7 days prior to delivery. Fetal head biparietal diameter and abdominal circumference were measured. The coefficient of correlation (r), and the ratio between estimated weight and actual weight were calculated. The coefficient of correlation was r = 0.954 between estimated weight and actual birth weight. The ratio between the two parameters was 1.025, the standard deviation 0.089. In our study, 41% of the antenatal estimated weights deviated less than 5% from the actual birth weight. For 72% of all estimated weights, the deviation was less than 10%. Ultrasonographic prediction of actual weight below the 10th percentile level showed a sensitivity of 85%, predictive value of 80% and specificity of 87%. In detecting inter-twin discordance > or = 20%, the respective values were 64%, 64% and 91%. Antenatal estimation of birth weight by ultrasound correlates well with the actual weights of twin fetuses. Prediction of individual fetal weight seems to be more accurate than prediction of inter-twin discordance.